Gablonz jewelry - Name for a variety of inexpensive glass imitation
jewelry from the town of Gablonz, Czechoslovakia.
Gachala emeralds - Characteristically
Chivor-like light-hued emeralds from a relatively new mine, in the Chivor area
gadolinium gallium garnet
- Diamond substitute developed by Bell Laboratories and marketed as Diamonique
II in 1975 by M. Landis Co. of New York, Inc. Weight more than twice that of
diamond (a stone the size of a 1.20-carat diamond is 2.75 carats); r.i., 2.03;
dispersion, .038; hardness, near 6.5.
gahnite - (gah'nite) Zinc spinel, dark green to black, in which zinc has
taken the place of magnesium. See GAHNO-SPINEL; SPINEL.
gahnospinel - A name which has been
proposed for the intermediate zinc-bearing magnesium spinel; blue, blue-green or
lavender in color, and slightly higher in refractive index and density than
gaining rate - In adjusting or
regulating timepieces; applied to timepieces that run faster than the standard
rate of time; opposite of a losing rate.
galalith - An artificial product made
from milk and formaldehyde, which is used to make horn-like products in
imitation of tortoise shell, ivory, amber, and jet.
gallery - Metals in strip form, for
making settings for stones in jewelry.
gallows tools - A cradle-shaped
tool with "V" notches to seat pinion arbors while its leaves are filed, shaped
galvanometer - An instrument for
detecting electrical current, its direction and intensity.
Gambia shell - A variety of pearl
oyster shell with a green nacre and nearly eight inches in diameter at a
maximum. Depending upon the exportation point it is known as Tahiti, Auckland or
Gambia shell; the same animal is scattered around the islands of the southern
gamboge - (gamm-boje) A natural gum,
soluble in water, used for a "resist" to paint over portions of a piece of
jewelry where a parti-colored design requires that no electroplating be
gangue - (gang) The non-ore minerals
associated with an ore deposit. Fluorite and apatite are frequent gangue
minerals of ore veins.
garden - Euphemistic description of the
flaws in an emerald.
garnet - A large mineralogical group of
silicates of complex composition, such as calcium-aluminum garnet (grossular),
iron-aluminum garnet (almandine) and so on. They occur in igneous and
metamorphic rocks, are among the commonest of gems, and are found in many
colors. They crystallize in the cubic system and are commonly found in crystals.
Common trade usage of the term refers to the red almandine and pyrope. See also
GROSSULAR; PYROPE; ALMANDINE; SPESSAR-TINE; ANDRADITE; UVAROVITE; DE-MANTOID;
gas bubbles - The rounded bubbles
seen in glass and synthetic stones which are taken as indicative of the origin
of the stone. Natural stones often contain angular cavities.
gasket - The plastic or rubber ring in a
water-resistant case to aid in its impermeability.
gate - Opening in a mold to permit entry
of molten material.
gathering pallet - A single tooth
on extension of a train arbor pivot in clock striking-work, that moves
successive teeth on the count-rack which determines the number of strokes
sounded at each hour. Also called TUMBLER.
gauge - A measuring device for
determining diameters, thickness, height, etc. See BOLEY; CALIPER; DOUZIEME;
GROSSMAN; LEVERIDGE; MICROMETER; SLIDE; VERNIER.
gauntlet bracelet - Wide, tapered
bracelet, worn above the wrist.
gauss. The unit of magnetic intensity of a magnetic pole at a distance of one
gearing - A device for transmitting
motion, consisting of interacting toothed wheels. See TRAIN.
gedanite - (jed'an-ite) A fossil resin
related to amber, but softer and lower in gravity. It contains no succinic acid
which is a requirement for true amber. The name is from Gedanum, Latin name for
gem - A stone cut and polished for use
in jewelry, which fulfills the requirements of beauty, durability and rarity.
The word is frequently used in the trade to signify a fine stone of unusual
quality. Sometimes used as a prefix to indicate rough from which a good stone
could be cut, as "gem crystal." Federal Trade Commission trade practice rules
forbid use of "gem" for a stone or pearl which does not possess the beauty,
symmetry, rarity and value to so qualify. Imitation stones and pearls may not be
described as "gems."
gem color - The perfection color
of any specimens. See GEM.
gem gravels - The gem
mineral-containing gravels resulting from erosion and soil removal of streams.
Found in stream beds or former stream beds, as in Ceylon, Montana, etc. As a
rule only a small percentage of the gravel pebbles are those of gem minerals;
quartz and rock pebbles usually predominate.
gem materials - Natural
substances favored for personal adornment because of their color, luster and
durability. Amber and jet are vegetable products; pearls, coral and ivory of
animal origin; the rest are mineral. See GEMSTONES.
Gemolite - Trademark of the Gemological
Institute of America for its diamond and gemstone illuminator-magnifier. It
combines wide-field binocular magnification with dark-field or
Gemological Institute of
America - A non-profit educational institution dedicated to the
advancement of the intellectual side of the jewelry trade. Gem-testing
laboratories, residential and correspondence-course teaching are included in its
services, together with gemological research and instrument development. Its
headquarters is in Santa Monica; its eastern headquarters and New York Gem Trade
Laboratory in New York.
gemologist - One who completes
recognized courses of study of gem materials and/or passes examinations that
demonstrate his competence to identify and evaluate gem materials. See GIA
GEMOLOGIST DIPLOMA; CERTIFIED GEMOLOGIST; GRADUATE GEMOLOGIST DIPLOMA; GRADUATE
gemology - The scientific, historical
and legendary study of gem materials, as distinct from all the minerals
scientifically studied in mineralogy. Frank B. Wade, an Indianapolis high school
chemistry teacher whose articles had been published in Jewelers' Circular, may
have been the first American to use the term. In 1916, in the preface to his
Text Book of Precious Stones for Jewelers and the Gem-Loving Public, Wade wrote:
"it is hoped. . . that the method of presentation used in this book will make
easy the acquisition of a knowledge of gemology."
Gemprint - Trade name for a method of
individualizing diamonds and other transparent faceted gems by photographing
their reflections; developed by Ephraim Frei, Shmuel Shtrickman and Charles
Bar-Isaac of Israel's Weitzmann Institute, and marketed by William Levine of
gemstone - A naturally occurring mineral
found in the rocks of the earth, the chemical composition and internal atomic
structure of which make it suitable for jewelry use: color, clarity, hardness,
rarity and availability. While only a handful of minerals-perhaps 20 out of
2500—have such properties, there are many gemstone names, because a single gem
mineral may have several gemstone varieties (e.g., the beryl family; emerald,
aquamarine, golden beryl, morganite, etc., are phases of a single colorless
mineral, beryllium aluminum silicate). The practice of separating gemstones into
two arbitrary groups-precious stones and semi-precious stones—has lost favor in
recent years; instead, all are termed gemstones.
generating circle - A circle
rolling on another, describing an epicycloidal arc, used to arrive at watch
tooth shapes. See EPICYCLOIDAL.
Geneva movement - Design of watch
in which upper pivot bearings are all in bridges or cocks, so as to expose the
entire train to view; also called bar movement or bridge movement design.
Geneva ruby - Misnomer for some
laboratory-processed rubies sold in 1882 and 1883 whose origin is still
uncertain, but which may have been made by melting small ruby fragments. Or they
may have been of Verneuil type made before that method was announced. They
disappeared from the market again as suddenly as they appeared.
geode - A partially hollow, rounded
nodule of stone, often crystal-lined. Agate and amethyst in particular
frequently occur this way. As a rule, the nodules are harder than the enclosing
rock in which they formed, perhaps filling in gas bubbles in a frozen lava flow,
and after their host weathers, they may be found as rounded hollow boulders. The
reference to the earth (geo) in their name refers to their rounded outline. See
German jasper - Common
irregularly-shaped jasper masses, as opposed to ball jasper, etc.
German lapis - Misnomer for
reddish jasper from Nunkirchen which is stained blue to resemble genuine lapis
lazuli. Probably identical with the so-called Swiss lapis.
German moccass - Imitation moss
agates, in which the pattern has been very skillfully placed on the stone. Their
perfection makes one suspicious, otherwise one would be likely to accept them as
genuine since they look so natural.
germanium - A whitish metal resembling
tin used in semi-conductors.
GIA Diamond Certificate -
Award from the Gemological Institute of America for completion of its
correspondence or residence course in diamond buying, selling, grading and
GIA Gemologist Diploma -
Award from Gemological Institute of America for completion of its correspondence
or residence courses on diamonds, colored stones and gem identifiation.
Gibraltar stone - A banded
light-colored onyx marble from a cavern at Gibraltar. See MEXICAN ONYX.
gilders' wax - A paste, used to
produce a rich color upon mercury-gilt work, made from oil and yellow wax, each
25 parts; acetate of copper, 13 parts, red ocher, 37 parts. The oil and wax are
blended by melting, to which the other substances, pulverized, are added
gilding - Coating any surface with a
film of gold. On non-metallic surfaces gilding is done by coating them with an
adhesive on which gold-leaf is laid. On metallic surfaces, gilding is done by
electroplating, or by fire-gilding. See ELECTROPLATING; FIRE GILDING; GOLD
FILLED; GOLD LEAF; VERMEIL.
gilding metal - A brass
containing less than the ordinary proportion of zinc, used as base metal for
manufacturing gold-plated jewelry and other wares.
gilt - Silver or base metal having gold
deposited thereon by chemical or electro-deposition process; now usually applied
to inexpensive articles on which the gold deposit is extremely thin. See GOLD
gimbals - A pair of rings pivoted
diametrically to each other and to outer and inner cases of a marine
chronometer, to keep the chronometer movement always level regardless of the
gimmal rings - A class of rings
dating from the first part of the 15th Century or earlier in which two rings are
joined by a pivot and united to constitute a single ring, or may be separated
and worn individually. Each circlet has a hand so placed that when both are
brought together the clasped hands unite the two rings. Usually the ring was
separated at the betrothal ceremony and the two parts worn by the betrothed
persons; after the marriage both were worn by the wife. Also spelled gemmel or
giogetto - (j'o'gett'toe) A black coral
from the Mediterranean. See ACCARBAAR.
girasol - (jeer'a-sole) A word with the
same significance as heliotrope, "sun turning." It has been used for fire opal,
in reference to the red or orange ground color of this material. It is also
applied to a transparent opal with a colorless ground mass and a bluish internal
opalescence. It is likewise a name which has been
used for moonstone.
girasol sapphire - A name given
to a sapphire cat's eye, a luminescent sapphire in which there is no pronounced
girdle - 1. The outermost edge of a cut gem, the dividing line
between crown and pavilion facets, the rim by which the stone is held in a
setting. 2. Diamond. The ideal diamond girdle leaves only enough
thickness to provide safety from chipping and a good setting edge thicker than
"knife edge." Its thinnest point might be about 1% of girdle diameter; its
thickest from 1.5% to 2% for diamonds over % carat and 2% to 2.5% for smaller
girdle facets - 1. The 32
triangular facets bordering the girdle of a round brilliant cut diamond, 16
above, 16 below. Also called break, cross, half, skew, skill facets. See UPPER
GIRDLE FACETS; LOWER GIRDLE FACETS. 2. If the girdle itself is faceted,
the stone is said to have a faceted girdle.
girdling - The process by which round
diamonds are given their circular or fancy shape, also known as cutting, bruting
or rounding. The diamond to be girdled is cemented to the chuck of a lathe with
resin and shellac. While it spins, a second diamond held in the dop of a 2-ft.
wooden tool is pressed against it. Fragments from both stones are caught below
the lathe chuck and used as diamond dust. To girdle a fancy shaped stone, the
lathe chuck can be made to run in an eccentric pattern. Before invention of
power-driven machinery in 1891, girdling was done by hand; "one diamond rubbed
against another until by mutual abrasion both take a form"-Benvenuto Cellini
gladstone - A covered serving dish made
of metal usually silver or silverplate. The cover is dome-shaped and mounted on
a pivot at each end so that it rolls back to uncover the contents of the dish.
glass gauge - A device for
measuring diameters and heights of watch glasses or crystals.
glassies -A diamond sorting grade;
crystals or glassies are perfect octahedrons of the best color.
glass, watch - A piece of any
transparent substance over the dial of a watch to protect dial and hands. Made
of glass, or plastic substance, to be "unbreakable;" also called watch crystal
regardless of material used in it.
glaze - Glassy mixture of mineral
substance with which a ceramic body is coated. In earthenware, it forms a
protective covering. In china, it blends with the body of the ware into one
glazier's diamond - Bort or small
crystals and corners for glass cutting.
gletz - Small cleavage cracks in a
glossing - Abrasive for producing high
polish on steel parts of timepieces; oxide of iron, pulverized and graded by
decantation. See DECANTATION.
glucydor - An alloy of copper and
beryllium used in solid balances and in hairsprings.
gneiss (nice) - A metamorphic rock,
essentially granitic in composition, but having a banded structure; a decorative
building stone and the matrix of some gems.
goethite - (ger'tite) Anhydrous iron
oxide often crystallizing in thin needles, which are then included in rock
crystal making a sagentic quartz; a common quartz inclusion, especially in
amethyst, mistakenly identified in Germany as cacoxenite, under which name it
has been sold in the trade.
going barrel - Mainspring barrel
in a watch, with gear teeth on its circumference; the barrel turns on barrel
arbor pivots, which are stationary except during winding of spring. See FUZEE,
going train - In striking clocks, the gear-train that is part of
the timekeeping side of the movement, as distinct from the striking train.
golconda - (goll-kon-dah) A term which is sometimes applied to old Indian
diamonds of fine quality. It is derived from the name of a city in the State of
Hyderabad, India, which was once a center of the diamond trade.
gold - A yellow-colored metallic element used for coins and jewelry since
prehistoric times. Most malleable and ductile of metals, gold may be beaten into
sheets as thin as .000003 inch and an ounce of gold may be drawn out into 50
miles of wire. Unalterable by heat, air or most corrosive agents, it forms one
of a group of noble metals; the metal is, however, dissolved by aqua regia, a
mixture of strong nitric and hydrochloric acids. Pure gold melts at 1063° C.,
and boils at about 2600° C.; its specific gravity is 19.3 and the chemical
symbol is Au. Pure or fine gold is too soft for ordinary use, and it is hardened
by alloying with copper, silver and other metals; alloys differ in their
hardness, color (red, yellow, green, white in many shades), ductility,
malleability, corrosion resistance and smoothness. See KARAT.
gold-backed - Jewelry made of laminated stock comprising an under
layer of gold, with a layer of platinum exposed to view, for platinum appearance
at less cost than solid platinum stock.
gold beating - The ancient art of
producing gold leaf. For sign-painting, lettering, etc., an alloy of 23 karat
gold is cast into small oblong ingots and reduced by a rolling mill to a ribbon
1/800 inch thick. Lengths one inch square are separated by ox membranes
(goldbeaters' skins), placed in a mold and beaten with a 16-pound hammer;
successive cuttings and beatings produce an extreme thinness. For certain
embossing an 18 karat alloy is used; for stamping hat-bands, 14 karat.
gold chloride - A combination of chlorine and gold, produced by
action of hydrochloric acid on gold; the resulting salt is largely used in
making solutions for gold electroplating.
gold electroplate - 1. A
coating by an electrolytic process with gold, or with a gold alloy of not less
than 10 karat fineness, to a minimum thickness throughout equivalent to
7-millionths of an inch of fine gold. (This means that where the fineness is
less than 24 karat the thickness must be proportionately greater, so that the
same amount of fine gold had been used.) If the coating is thinner than
7-millionths of an inch, it may be marked "Gold Flashed" or "Gold Washed." If
the coating is equivalent to 100-millionths of an inch of fine gold, it may be
marked "Heavy Gold Electroplate." 2. Watchcases. Watchcases electroplated
with gold or gold alloy to a minimum thickness of 3/4/1000ths of an inch are
marked "Gold Electroplate" or "Gold Electroplated," optionally preceded by
designation of the karat fineness of the gold alloy. Example: "18 Karat Gold
Electroplate." A thickness of I^/IOOO of an inch or greater may be described as
"Heavy Gold Electroplate," optionally preceded by designation of karat fineness
of the gold alloy. See ELECTROPLATING.
golden beryl - Yellow to
gold filled - A plating by
soldering, brazing, welding or other mechanical means of gold alloy of not less
than 10 karat fineness, when the plating constitutes at least l/20th of the
weight of the metal in the entire article. Synonyms: "Gold Plate," "Gold
Plated," "Gold Overlay," "Rolled Gold Plate." The term must be preceded by the
karat fineness of the plating, such as "14 Kt. Gold Filled," "14 Kt. G.F.," "14
Kt. Gold Plate," "14 Kt. G.P." or "14 Kt. Gold Overlay." When such plating
weighs less than l/20th of the metal in the entire article, the term "Gold
Plate," "Gold Plated," "Rolled Gold Plate," or "Gold Overlay" is preceded by a
fraction showing the relative weight of the plating to all the metal in the
article. Example: "l/40th 12 Kt. Rolled Gold Plate" or "1/40 12 Kt. R.G.P." 2.
Watchcases. With watchcases, "Gold Filled" designates a similar plating of not
less than 3/1000" in thickness. Example: "12 Karat Gold Filled" or "12 K G.F."
"Gold Plate" or "Roiled Gold Plate" designates such watch-case plating not less
than 1.5/1000" in thickness. Example: "10 Karat Gold Plate" or "10 K. R.G.P."
gold flashed - Designation for a
gold electroplate thinner than 7-millionths of an inch of fine gold. Synonym:
gold leaf - See GOLD BEATING.
gold nugget - A water-worn mass
of vein gold found in a stream bed or former stream bed. More or less rounded
depending upon the amount of wear and distance of transportation.
gold opal - An alternative name
for FIRE OPAL, possibly somewhat lighter and more yellowish in tone.
gold overlay - See GOLD FILLED.
gold quartz - Usually a
milky-looking quartz containing streaks and masses of gold. Often polished and
used as a gem, especially in gold-producing regions.
gold scales - A pair of
balance-scales, well made but usually not of precision type, for use with Troy
weights, in the jewelry trade. Modern gold scales are electrically controlled,
extremely accurate and readings noted on an electrically illuminated dial in
ounces, pennyweights and grains or ounces and thousandths of pennyweights, Troy.
goldsmith - A worker in gold; a jeweler.
gold smudge - See BLACK
gold solder - An alloy usually
composed of gold, silver, copper and zinc and sometimes cadmium—and sometimes
nickel in white solders-used for hard-soldering gold work. It has been the
custom in the U.S. jewelry industry to use solders of lower karat fineness than
the article to be soldered, and the stamping laws allow an extra margin in the
fineness of the whole article, to provide for this. The practice has been
rationalized by the belief that a lower karat solder is necessary in order for
the solder to have a melting point safely below that of the article to be
soldered. There are many who doubt the necessity for this. Solders with
adequately low melting points can be produced for every commercial karat level,
at the same karat. The lower karat solders have been eliminated in some European
countries and in the mid-70's were under attack in the U.S.
gold-spring - In chronometer escapement,
a flexible strip of gold, fastened at one end to detent-body, its free end
protruding slightly beyond end of detent, to be pressed against by unlocking
jewel for unlocking the escapement, the gold-spring giving way at alternate
beats to allow a "dumb vibration," when
escapement is not unlocked and no impulse is given. See PASSING SPRING.
goldstone - See AVENTURINE.
gold topaz - Erroneous name for light yellow-brown quartz. See
TOPAZ and SPANISH CITRINE.
gold washed - Designation for a gold electroplate thinner than
7-millionths of an inch of fine gold. Synonym: gold flashed.
goniometer - (gon'nee-om"meet-er) An instrument for measuring the angles
between the plane faces of a solid, usually crystals. Gemologically it can be
used for measuring the angles of facets and for determining the refractive index
of transparent solids, and of immersion liquids.
goodletite - Australian-New Zealand term for a green pyroxene or
amphibole matrix with ruby corundum through it. Similar, on a smaller scale, to
the Tanzanian green zoisite matrix with the large rubies at Longido. Goodletite-like
rock has been found in North Carolina.
gooseberry stone - Grossular, in reference to a common
yellow-green color of this garnet species, whose name is derived from the Latin
name for the gooseberry family.
gorgulho - Brazilian term for diamond-bearing quartz gravel river
goshenite - (go'shen-ite)A colorless beryl, originally named for Goshen,
Mass., where some was found.
gota de aceite - "Oil drops," the first quality of emerald.
goutte d'eau - (goot doe) Colorless topaz, "drop of water."
goutte de sang - (goot-duh-song) Red spinel, "drop of
gouverneurite - (goo-vair-noor'ite). Brown magnesia tourmaline from
Gouverneur, N.Y. See DRAVITE.
grading systems (diamond) - See CLARITY GRADE; COLOR GRADE;
Graduate Gemologist Diploma - Award from Gemological
Institute of America to holders of the GIA Gemologist Diploma for completion of
its two one-week resident classes in diamond appraisal and gem identification,
offered in Los Angeles and other cities across the country.
Graduate Gemologist Residence Diploma - Award from
Gemological Institute of America for completion of its 26-week resident training
program in Los Angeles or New York, offering laboratory work in both diamonds
and colored stones.
graffito - Enameled surface into which a design has been scratched before
firing. See ENAMEL.
Graham escapement - Clock
escapement invented by George Graham, of London, Eng., about 1715; principal
characteristic is pallets with locking faces concentric with pallet center,
making of it a dead-beat escapement. See DEAD-BEAT ESCAPEMENT.
grain - 1. The earliest unit of weight, originally a grain of
wheat or barleycorn, and the smallest unit in the Troy, apothecaries and
avoirdupois systems. In the Troy system, long used for precious metals, 24
grains (gn.) = 1 pennyweight (dwt); 480 gn. or 20 dwt. = 1 ounce Troy; 5760 gn.
or 240 dwt. or 12 ounces Troy = 1 pound Troy (1 Ib t). 1 grain = 64.798
milligrams; 15.432 gn. = 1 gram. 2. Unit of weight for pearls, equal to
one-fourth carat; therefore, four pearl grains = one carat. 3. Term
commonly used in diamond polishing to refer to cleavage directions. 4. In
speaking of opal, it refers to the pattern of color flashes, for example:
harlequin, bands, triangles, squares, etc.
grain marks - Also known as grain lines, knot lines or twinning
lines, they represent a difference in grain direction across a twin plane; they
may appear on the surface or within a fashioned diamond.
grain tin - The purest variety of block tin, advisable for use in
making laps for polishing steel watch parts with rouge or diamantine.
grainer - A loose term for diamond weights in quarter-carat multiples;
e.g., a stone that weighs about one quarter carat is sometimes referred to as a
grainer; or one that weighs about three-quarters of a carat as a three-grainer.
gram - Unit of weight in the metric system, based on the weight of one
cubic centimeter of water. It is equal to 15.432 Troy grains. One kilogram, 1000
grams, equals 2.2046 pounds.
grande sonnerie - (grahnd'shon'uh'ree') Grand or full strike in
clocks that strike quarter-hours. First the hour is struck on a single bell or
gong, followed by a ting-tang on two gongs or bells for each quarter. Thus at
8:45, eight single strokes are sounded, followed by three ting-tangs (double
strokes). Some strike the hours and four quarters on the hour.
grandite - A coined combination of grossular and andradite suggested for
garnets of composition intermediate between the two.
granite - A fairly coarsely crystalline rock composed essentially of
potash feldspar and quartz, usually with a few accessory dark minerals like
mica, etc., usually formed by slow cooling, at depth, of a molten magma. See
granulating - Forming melted metals into grains for alloying, by pouring
the metal slowly into a large vessel of water.
granulation - An ancient jewelry art by which small gold particles adhere
to the surface without evidence of solder. Grains or minute spheres of gold used
in granulation are formed by placing small pallions of gold between layers of
powered charcoal in a covered crucible or iron box and heated in a furnace until
melted. This produces perfectly formed spheres of unoxydized gold.
graphic granite - An intergrowth of large crystals of quartz and
feldspar found in pegmatites, in which the quartz crystals are so arranged that
their cross-sections resemble cuneiform writing. Also known as HEBREW STONE. See
graphite - Natural crystalline carbon, used for making crucibles for
melting metals in jewelry work and to a limited extent as a component of
lubricants for clocks. Black specks in diamonds are often called graphite.
grasshopper escapement - Invented by John Harrison (1693-1766),
the action of levers and counterweights was ingeniously arranged so that no oil
was required. Its action was similar to the slow-motion movement of a
graver - A cutting tool used by hand, for engraving, or for turning work
in a lathe. See BURIN.
graver sharpener - Tool for guiding gravers being sharpened on
oilstone to produce dead-flat faces; essentially an adjustable graver holder
mounted on a roller which rolls on the oilstone and guides the work.
gravity escapement - Clock escapement in which impulse is given
pendulum directly by a weight, which is lifted previously by power from the
train; principally used in tower clocks; invented by E. B. Denison, 1851, for
the "Big Ben" clock on Parliament buildings, London.
gray finish - 1. Horology. A type of finish for metal parts
of timepieces, of a frosted or matted appearance, produced by rubbing a part on
abrasive grains on a lap, so that the grains roll between the work and the lap
and indent the work with a multitude of microscopic pits. From this we have also
a term, "in the gray," referring to a watch or a group of its parts that are
fitted to each other in working order, but not yet given their final finish.
2. Silver. See BUTLER FINISH.
grease table - Device for catching diamonds used on the sorting
tables and invented (1897) by George Labram and F.B. Kirsten. Diamonds alone of
all the minerals contained in the blue ground adhere to the grease, while all
others flow away with the water as tailings over the end of the percussion
table. This gem-separator proved unsuccessful with rubies at the Burma Ruby
grease wheel - A felt wheel buff, charged with abrasive mixed with
heavy grease, for use on jewelers' lathes for preparing metal surfaces for
great wheel - In a watch or clock, the toothed wheel that gears
with the center pinion; the "first wheel" in a timepiece train, as: the toothed
part of a going or motor barrel, fuzee, clockweight drum, etc. See TRAIN.
Greek key pattern - A pattern or border composed of lines
or narrow fillets at right angles to each other, commonly known as Greek fret
green chalcedony - An imitation of chrysoprase made by artifically
green ear - Name given to a river pearl.
green garnet - Demantoid, uvarovite, or grossular. Erroneously
applied to green enstatite from South Africa.
green gold - Gold alloy containing a relatively high proportion of
silver. Eighteen karat green gold consists of 75 per cent fine gold and 25 per
cent fine silver; green gold alloys of lesser gold content contain relatively
small amounts of zinc and copper, besides silver.
green jasper - Jasper commonly used in Chinese carvings but coming
from Siberia and colored by chlorite of iron.
green John - Green fluorite. See BLUE JOHN.
green quartz - Erroneous trade name for the green fluorite of
which many decorative Chinese carved objects are made. See AVENTURINE.
green onyx - Trade name for green-dyed chalcedony.
greenovite - Sphene, colored rose by manganese, and rarely, if ever, seen
in gem quality.
green starstone - CHLORASTROLITE.
greenstone - Nephrite, but has been used for chlorastrolite.
grenalite - STAUROLITE.
grey gold - A pale-colored alloy of gold and iron; or gold, iron
grinding - The rough shaping of a gem, in preparation for the polishing.
grinding lap - A piece of metal or other substance, shaped to
reproduce its form on pieces of work, by action of an abrasive spread on the
lap. To grind square or conical pivots, laps are shaped like files and used by
hand; or are cylindrical, etc., for use on rotary pivot polishers; or are of
large flat area for flattening surfaces of work rubbed on lap by hand. Laps for
grinding watch jewels are made of copper charged with diamond powder.
grindstone - Abrasive wheel of natural stone, used with water for
rough-shaping steel cutting-tools preparatory to sharpening on oilstone.
grommet - A metal ring surrounding a hole.
groove - The seat turned in top of mainspring barrel wall, into which
barrel cover is snapped to fit; also the seat turned in watchcase bezel for
Grossman gauge - A caliper gauge for measuring, in millimeters,
tenths and hundredths, diameters of the smaller parts of watches, such as
grossular - (gross'u-lar) A calcium aluminum garnet, usually light in
color and including the gem hessonite. Grossular had been restricted to
colorless, pale green and brown to rose red until the Nineteen Seventies when
transparent green, with some advantages over emerald, was found in Tanzania and
Kenya. Elsewhere, most of the gem pebbles come from Ceylon, where the brown
crystals resemble and are confused with zircon. Few other localities produce
stones which can be cut. A light green massive variety, somewhat resembling
jade, has been found near Pretoria, South Africa, and has been sold under the
name Transvaal jade, falsonephrite, African jade, garnet jade, etc. See
GOOSEBERRY STONE, TSAVORITE.
guanin - (gwa'neen) The substance extracted from fish scales which is
responsible for the iridescence of imitation pearls made of the essence d'orient.
guard chain - Originally, a long silver or gold chain from which
keys, watch, or other object hung. In modern times a small chain attached to one
end of a neck chain or bracelet; the other end of the chain is connected to a
spring ring which engages a link on the opposite end of the bracelet or
necklace. This is to prevent the loss of the jewelry should the snap or clasp
open. See SAFETY CHAIN.
guard pin - In single-roller lever escapement, the pin set
perpendicularly to the lever, that provides safety-action in connection with the
edge of the roller table. See LEVER ESCAPEMENT.
guard point - In double-roller lever escapement, the metal finger
set on the fork parallel to its top, projecting toward rollers, and that
provides safety-action in connection with edge of safety-roller. See LEVER
guard-ring - A thin ring, inconspicuous in appearance, to wear on
finger in front of a valuable ring, to prevent the latter slipping off. Guard
rings are often worn in pairs, with or without stones, on each side of a wedding
guard shake - In lever escapement, the freedom or play between
guard-pin or guard-point, and the edge of the roller table. The amount of guard
shake is measured as the angle of fork motion allowed between resting of
fork-lever on a banking, and contact of guard pin or point against the roller
guarnaccino - Vermeille garnet.
gudgeon - The shaft of a clock or lathe upon which a wheel or pulley
Guides for Watch Industry - Adopted by the U.S.
Federal Trade Commission May 14, 1968; amended Aug. 18, 1970.
guilloche - (gee-losh’) Decoration engraved on watch cases or jewelry by
machinery; engine-turning; geometrical designs engraved as a base for decoration
with translucent colored enamel, through which engraving can be seen.
gum anime - (gum-ah-neem') A recent fossil resin, often containing
insects. See COPAL.
gum tragacanth - (gum-trag'ah-kanth) A natural gum, soluble in hot
water, used for holding small parts of jewelry together in preparing for
soldering; sometimes added to borax-and-water flux for the same purpose. Also
used as an adhesive for holding ground enamel to metal before firing.
gunmetal finish - A deep blue-black finish used on watch cases,
jewelry, etc., produced usually by electroplating a coat of iron on the work,
then coloring the iron in a chemical bath.
gut pallet - A silent escapement using gut across a cage-type
anchor for the pallets similar in effect to a pin-pallet escapement.
gypsum - (jip'sum) A soft hydrous calcium sulphate, number two on the
Mohs hardness scale, but commonly used in decorative carvings, currently in
orange, satin spar figures from the USSR. Alabaster is a variety of gypsum, as
is much satin spar. "Alabastra" of the ancients included calcite, as well as
gypsum. The name alabaster was derived from the Greek name for an Egyptian town.
It is usually white or light colored, but is often dyed many bright colors. See
ALABASTER; ATLAS SPAR; SATIN SPAR; SELENITE.
gypsy setting - Usually refers to a complete one piece mounting
consisting of a round shank running into a heavy top. The diamond or other
precious stone set in the top is held in place by burnishing or hammering the
metal over the entire girdle of the stone.
gyration, radius of - In a watch balance, the mean distance of the
effective weight of all parts of the balance from its center of rotation.
H - The chemical symbol for hydrogen in a formula, but in referring to
gems, it usually means "hardness." See HARDNESS.
habit - Crystallography. The overall appearance of a crystal; for
example, an elongated beryl crystal is said to have a prismatic habit, the usual
diamond crystal to have an octahedral habit. Fluorite is sometimes octahedral
and sometimes cubic in habit.
hack-saw - A frame saw for rapid cutting of thick metal, of heavier
construction than a jewelers' saw, used with teeth of blade pointing forward
instead of toward the handle.
hack watch - 1. Any watch whose balance can be stopped to be
synchronized with an accurate time source. 2. A watch used between ship and
shore in seaports, for setting marine chronometers to time from an accurate
clock on shore.
haematite - A British spelling of hematite.
haft - The handle of a knife or tool.
hailstone - A ball bort, found especially at Bultfontein, which is
composed of alternating layers of gray and clear, poorly and well-crystallized
hair - A type of inclusion in a gem, resembling a hair. It may be due to
the presence of a slender needle-like crystal or of an etched tube, as sometimes
seen in kunzite.
hair amethyst - Sagenitic amethyst; black needles in this type of
material coming from Montana are tourmaline.
hairspring - A metal spring of spiral, helical, or combined form,
attached to balance of a watch, to govern its motions; the balance and the
spring together constitute the "balance-assembly," which is the true timekeeping
element. See BREGUET HAIRSPRING; FLAT HAIRSPRING; HELICAL HAIRSPRING.
hairspring tweezers - See HAND-MADE TWEEZERS.
hairspring vibrator - A device for holding blank hairsprings while
counting beats for selecting a spring to match balance with train; the
vibrator usually comprises a standard-beating balance for comparison with the
beating of the spring being tested.
hairstone - See SAGENITE.
half-and-half solder - Trade term for soft solder of the alloy, half tin
and half lead, used for average work. For special purposes, involving certain
contacts, etc., this formula may be varied, using more lead or more tin. See
half-bored pearl - pearl drilled only partly through for use as pendant
rather than as a bead.
half-brilliant - diamond cut without a lower part, the top brilliant cut,
the bottom, one large culet. In a sense, it is a rose with a brilliant cut. See
half-chronometer - term used in England meaning a highly adjusted pocket
watch with lever escapement.
half Dutch rose, half Holland rose - A
rose-cut stone with 18 triangular facets in the crown. See HOLLAND ROSE; ROSE.
half-dead-beat escapement - A clock escapement with its recoil, a
compromise between dead-beat and full-recoil beat.
half-hunter - A watch case of the hunting type, with a glazed opening in
center of lid through which parts of the hands are visible, with numerals
enameled around the circumference of the opening. This kind of watch case has
its greatest popularity in England. It is meant to combine the ruggedness of a
hunting case with the convenience of open-face case. See DEMI-HUNTER
halfmoon - A fancy diamond shape, the girdle outline of which is
half-open tailstock - Tailstock for American type watchmakers' lathe with
upper half of spindle-hole cut away, to ease the motion of spindle for sensitive
use in drilling; or to enable quick exchange of spindles for different uses.
half-pearl - A round pearl sawed in half. Also used to describe a
Japanese culture pearl type, which is made from a pearl grown against the shell,
instead of free, cut out and attached to a mother-of-pearl hemispherical bead of
the same diameter, to make a perfect sphere. These pearls preceded the modern
entire culture pearls. See MABE; CYST PEARL.
half-pearl work - In jewelry making, the setting of small, hemispherical
pearls close together, in circles, curves, or other designs, set in
flat-bottomed recesses, the upper corners of which are usually pressed or beaded
inwards to fasten the half-pearls.
half-round file - A file whose cross-section has one flat and one convex
face, gradually larger from point to tang.
half shell - The portion of a cylinder in cylinder escapement that
forms the lips which act as pallets. See CYLINDER ESCAPEMENT.
half-timing - Running a lever escapement watch without the hairspring in
place. Reversal of balance motion is effected by rebound of the roller jewel
from outside the fork-horn; the long arc of balance motion required to do this
is taken as indication of good adjustment of escapement.
Halifax moon clock - Clock showing lunar phases with the
turning of an actual globe, half blue, half white, showing in an aperture,
instead of the usual moon disk.
Haliotis pearls - See ABALONE
Hallmarking Association -
International organization of administrative members of state-recognized
hallmarking authorities for precious metals (bureaux de garantie)', established
in 1965, to promote uniformity, protect hallmarks (poincons de garantie) from
forgery, and further international cooperation in hallmarking.
hambergite - A rare beryllium borate
found in colorless gemmy crystals in Madagascar. It is interesting only to
collectors of rare gems, but has a very strong birefringence, which is exceeded
among the gems only by sphene and cassiterite. The refractive index ranges from
1.553 to 1.631, but the dispersion is low and a cut gem resembles rock crystal.
Hamilton metal - A brass alloy
made of equal parts of copper and zinc, long used as an imitation of gold.
hammer - In metalwork, a device for
beating metal. In jewelry and silversmithing hammers are used for forming,
stretching, embossing, raising, riveting, planishing, peening and chasing.
hammer, ball peen - Hammer with
polished, rounded head used for peening, hardening or decorating metals.
hammer crank - Lever on arbor
through which power is transmitted from striking train of a clock to raise
hammer from bell or gong.
hammered - A form of metallic decoration
obtained by repeated taps on the surface with a small hammer. See HARDENING.
hammer-hardening - Horology. Operation
for making brass springs, in clock work, stiffer and more resilient, by
hammering on anvil to condense the grain of the metal.
hammer-pallet - In a repeater watch
mechanism, the tooth that raises the hammer by pressing on the hammer-tail.
Baroque-shaped like the
head of a hammer.
hammer tail - The rear ex tension
of a pivoted hammer in a striking clock acted upon by the hammer spring.
hand buff - A stick covered with
emery paper, or felt or leather charged with abrasive powder, or a solid
abrasive slip, for light grinding and polishing operations in jewelry work and
hand drill - One of a class of
drills used in jewelry work and horology, including a drill-point in a spindle
driven by a bow, a torsion cord, gearing, or a helical thread on a spindle
engaging a sliding nut for rotating the drill.
hand-feed sliderest - A sliderest for a
watchmakers' lathe, to hold and operate a cutting tool, operated by a handcrank
instead of by a shaft geared to the lathe spindle. See SCREW-CUTTING SLIDEREST.
hand-filled print - In the decoration of
dinner-ware, a combination of decal and
hand painting - The design is applied by decal and the colors are
filled in by hand.
hand gauge - A plate with linear markings for length as well as
with a tapered needle to determine hole sizes of watch hands.
handless watch - Watch with dial on which time is shown by
numerals appearing in openings in the dialplate; the numerals are on rotating
discs under the dial.
hand-made - It is an unfair trade practice to represent that a product is
hand-made or hand-wrought unless its entire shaping and forming from raw
materials and its finishing and decoration were accomplished by hand labor and
manually-controlled methods which permit the maker to control and vary the
construction, shape, design and finish of each part of each individual
product.—From Rule 11, Federal Trade Commission, Trade Practice Rules for the
hand-made tweezers - A trade term meaning tweezers of fine steel and
workmanship, especially sensitive and firm-gripping, used for hairspring work
instead of for ordinary handling of watch parts. It is characteristic of
hand-made tweezers that they are not electroplated, but show the natural surface
of the hardened and tempered steel.
hand-pressed glass - Glass that is individually formed in a mold, by
means of a plunger forcing the glass mixture into the desired shape.
hand remover - Tools for taking hands off watches, of various
forms but all working on the principle of a pair of wedges to exert force
without damaging dials or hands.
hand-rest - On a watchmaker's lathe, an adjustable rest to support a
cutting tool for hand-turning, distinguished from the sliderest with its
mechanically operated cutting tool; also called a T-rest. See SLIDE-REST.
hands - The pointers that turn around the dials of timepieces, indicating
hours, minutes and seconds. Early clocks and watches had only an hour hand; the
concentric minute hand was introduced shortly after 1650; and the seconds hand
hand-setter - An item of clock material; a split tube with a knob on one
end, placed permanently on the time and alarm hand arbors of alarm clocks for
setting the hands.
hand-spring - A spring on' the minute hand arbor of English and Colonial
American clocks, bearing against the under side of the minute wheel; overcoming
its tension permits setting of the clock hand to time.
hand tongs - Special form of pliers, with graduated holes, for
holding watch hands while filing or broaching holes larger.
hand-train - English term for dial train.
hand vise - A small vise similar to a bench vise but with its
elongated base set into a handle.
handwheel - On the American-type watchmakers' lathe, a wheel on the
draw-in spindle for tightening chuck on work.
hand wrought - A term used to indicate that an article, so
stamped, is made and decorated from a flat sheet of metal entirely by hand tools
without the aid of machinery.
hard enameling - A class of enamelwork used decoratively on
jewelry, watch cases, etc., and for numerals on timepiece dials, in work of the
finer grades. Characteristic of hard enameling is that the work and the
pulverized applied enamel must be brought to a high heat for flow and adherence.
The enamel is a species of glass, usually colored; after it is melted on the
work, the surface of the enamel is usually ground and polished. See ENAMELING.
hardening - A method whereby tool steel is heated to cherry red,
approximately 1400°F, and quenched in water or oil. Steel so hardened is too
hard for most purposes, so it is then tempered to the hardness and toughness
desired. 2. Other metals may be hardened by alloying or hammering.
hard mass - An unusually hard glass used in imitation gems.
Erroneously applied to synthetic spinel.
hardness - In reference to gems and minerals, this is defined as the
resistance offered to abrasion or scratching. It is of great importance in gems,
for their durability depends in large measure upon their hardness. See MOHS
hardness pencil - A pointed instrument containing one of the
minerals of the Mohs scale, used in testing for hardness by scratching.
hardness scale - See MOHS SCALE.
hardness wheel - An instrument for testing hardness, like the
pencils, but with the points set like spokes in a wheel, a form in which the
hardness pencils are frequently used by jewelers.
hard platinum - Alloy usually of pure platinum and 10 per cent
iridium, used for jewelry, etc., as being more wear-resistant than soft pure
platinum. Since World War II, 5 per cent ruthenium has been used as a hardening
agent. Other hardeners have been suggested such as osmium.
hard soldering - Classification of soldering operations in which
parts to be joined must be heated red-hot to fuse hard metal used as solder,
making a stronger union than with softer solders fused at a lower heat. See
Hardy's balance - Balance invented about 1800 by William Hardy and
used in marine chronometers, characterized by high vertical attachments to the
balance designed to reduce middle temperature error.
harlequin opal - A precious opal characterized by broad, sharply
demarcated flashes of varying hues, often separated by a more or less
harmonic motion - The tendency to assume motion by objects of the
same natural frequency, mass or active length when influenced by others.
Example: When a descending weight nears a clock pendulum, it may swing in a
direction opposite to that of the pendulum.
harp handle - A type of handle used on presentation cups of Irish
origin. The handle resembled a harp.
Hartnup's balance - A mid-19th Century chronometer, split-arm
balance but with continuous spokes terminating in an inverted bezel-rim,
designed to reduce middle temperature errors.
hatchet stone - Nephrite. See AXE STONE.
Hauynite, haiiyne - (ha'win-ite) An isometric sodium aluminum silicate,
containing some sulphur; lapis lazuli can be regarded as a variety of this
mineral. Named for the Abbe Rene Just Hauy, a famous French mineralogist of the
late 18th and early 19th Century. See LAPIS LAZULI.
hawaiite - A pale green chrysolite or peridot found in Hawaii. See
CHRYSOLITE; PERIDOT. Its use is highly undesirable, for not only is it a word of
no significance in this relation, but it also tends to be confused with a
particular type of basalt which has been named hawaiite by petrographers.
hawkbill - Heavy, curved-nose pliers used by silversmiths to hold work
being beaten to form on bench block, etc.; also lighter pliers used in jewelry
hawk-eye - A variety of quartz containing parallel bluish-green needles
of amphibole. When cabochon-cut, the gem exhibits chatoyancy. See TIGER EYE.
haystack - An American name for a high-domed button pearl.
head - The upper portion of a ring,
mounted or to be mounted on a shank. It consists generally of a tapered box
having prongs or other means of fastening a stone.
header - Punches in a staking set, for making rivets on turned
countersunk shoulders, or on end of fitted rivet blanks.
headless screw - A set screw with the slot cut into the top of the
threads without a head such as a side, dial screw.
headstock - On a watchmakers' lathe, the attachment to the bed that
contains the bearings for the spindle that carries the work. See TAIL-STOCK.
heart cam - Cam in the form of a heart; invented by Adolphe
Nicole, 1862. Used in chronographs; the cam, attached to the arbor carrying the
hands, causes them to return to zero when a "hammer" strikes the cam.
heart-shaped brilliant - A variation of the brilliant related to the
pendant-cut brilliant, with the round end flattened, and the girdle broadened
until its length about equals its breadth. Cullinan 5 was cut in this way.
heart-shaped emerald - A variety of the emerald cut.
heat-and-cold adjustment - In watches,
the exact distribution of weight around the balance rim, to effect compensation
for changes in the timing rate that are caused in the hairspring by changes in
heated stone - A stone that has been treated by heat to change its
color, at the mine or, after cutting, in electric ovens with the stones embedded
in sand. The temperatures and precise methods frequently are regarded as trade
secrets. Some white chalcedony becomes carnelian; amethyst and smoky quartz
become citrine; some greenish yellow, greenish blue or brownish yellow beryl
becomes aquamarine; some reddish brown topaz becomes pink to violet pink; some
dark green tourmaline becomes light green; brown zircon becomes blue, golden
brown or colorless; some tanzanite achieves a rich blue. No simple tests exist
for detecting such heated stones.
heat shield - Trade name for a heat-resistant substance that
prevents heat from reaching protected areas. Eliminates the need for removing
stones while soldering.
heat-tinting - The gradual building up of a film of oxide on steel by
heating to produce various colors as a finish, rather than for working temper.
Mainsprings are always first tempered blue; but sometimes then de-colored and
reheated to produce shades of brown or purple, for appearance sake; this is
heat-tinting, as distinguished from tempering. See HARDENING; TEMPERING.
heat-treatment - 1. Metallurgy. A term broadly covering all
operations for the purpose of altering the nature and conditions of metals for
various uses; for example, hardening steel; tempering steel; annealing steel;
case-hardening, etc. See ANNEALING; HARDENING; TEMPERING. 2. Gemology.
See HEATED STONE.
heavy - A quality grade of sterling silver flatware
offered by many American silversmiths until introduction of the place setting in
the Nineteen Thirties. Heavy sterling flatware was in terms of 12 Troy ounces of
sterling silver per dozen teaspoons. See MEDIUM; LIGHT.
heavy gold electroplate - A coating or plating, affixed by
an electrolytic process, of gold or of a gold alloy of not less than 10 karat
fineness, the minimum thickness throughout of which is equivalent to 100
millionths of an inch of fine gold. 2. Watchcases. Watchcases electroplated with
gold or gold alloy to a minimum thickness of 11/2/1000 of an inch or greater are
marked "Heavy Gold Electroplate," preceded by designation of karat fineness of
the gold alloy. Example: "16 Karat Heavy Gold Electroplate." See GOLD
heavy liquids - High density liquids, such as bromoform and
methylene iodide, which are used in the determination of gem stones by noting
whether the gem in question floats or sinks in liquids of known specific
heel - 1. The back corner of the lifting plane on a club tooth of
an escape wheel of a lever escapement. See CLUB TOOTH; ESCAPEMENT. 2. The
angle formed on the bottom of a graver, at the cutting end of the tool to
control the depth of an engraved line.
heel ball - Soft black wax used for filling engraved letters and
numerals on clock dials, inscription plates, etc., by rubbing in the cold wax;
used where heating for harder enamels would spoil finish on work.
height gauge - 1. Part of a watch crystal gauge that
measures the vertical space inside the crystal for clearance for hands. 2.
A measuring instrument for determining lengths of shoulders, etc., on arbors
heishi beads - (hee'she) Small oceanic shells strung as beads
through a center hole that may be natural or drilled, offered in a variety of
natural or dyed hues; simulated, also, in plastic. Used in costume jewelry in
the U.S. after 1974.
helical gears - Pinions with leaves set at an angle with the axis;
used in Swiss-type music boxes, and in "worm-gear" escapements.
helical hairspring - A balance spring with coils wound in the form
of a cylinder instead of a spiral, used mostly in marine chronometers
heliodor - An undesirable name for yellow-green beryl. Originally
proposed for the beryl from Southwest Africa, it proved impossible to show that
it was any different from any other beryl of this hue; the simple descriptive
is less confusing and preferable.
heliolite - Sunstone. Also see AVENTURINE,
heliotrope - Bloodstone; this name refers to an ancient legend that the
reflection of the sun in water in which this stone had been placed was turned
red, hence, "sun turning.”
hemachate - Said to be a light-colored agate spotted with red jasper, and
also known as blood agate. It is an improbable looking word for English and
seems to be the result of a confusion of languages. Hemagate would be more
likely and equally unnecessary.
hematinon - (he-matt'i-non) A dark red glass used in the earliest times
and said to be a stage in the preparation of aventurine glass. Also known as
hematite - (hemm'-ah-tite) An oxide of iron and one of the principal ores
of that metal. It may be hard and black and opaque, when it is sometimes used as
a gem, or it may be soft and bright-red, when it makes a pigment, especially in
paints. Even the blackest material gives a red streak when scratched across an
unglazed porcelain tile, hence, the name given by the ancients, "bloodstone,"
now no longer applied to this mineral. Also very wrongly called black diamond.
See ROUGE; ALASKA DIAMOND.
hemimorphite - A silicate of zinc and a common constituent of oxidized
zinc ores. Formerly known as calamine, great confusion has resulted from
erroneous interchange of that name with smithsonite, the carbonate of zinc, and
this new name has been substituted. The mineral crystallizes in orthorhombic
crystals which are different at the two ends, or "hemi-morphic"; as in
tourmaline, heating charges one end positively and the other negatively.
Gemologically it is probably of interest only to collectors or as a constituent
of a smithsonite-hemimorphite mixture. Colorless when pure, yellowish and
bluish-green pieces have been found suitable for cabochon cutting.
Herapathite - The active constituent of polaroid, named for the
discoverer of the quinine iodo-sulphate, W. B. Herapath, who, in 1851 first made
the compound, but who was unable to put it to practical use.
Hercules stone - Lodestone.
Herkimer County diamonds - Misnomer for rock crystal from
Herkimer County, New York. Small brilliant colorless crystals are found in
pockets in a dolomite and have been widely distributed, usually uncut, under
this name, which, while it probably deceives no one, is highly undesirable
hermaphrodite calipers - A caliper which can measure both inside
and outside diameters.
hertz - A frequency unit equal to cycles per second; symbol: Hz. Example:
megahertz, one million cycles per second.
hessonite - (hess'on-ite) The proper name for the yellowish to
reddish-brown variety of grossular garnet, derived from a Grecian word for
"less," which refers to its hardness in relation to the brown zircon, hyacinth,
with which it is perpetually confused. It commonly has a granular internal
structure which is visible through a lens. Often found in Ceylon, in association
with zircons, also in California. Known as Ceylon hyacinth, false hyacinth and
more commonly as cinnamon stone or essonite.
hexagon - A gem shape, a square hexagon is equi-dimensional while the
blind hexagon has two parallel shorter sides, and the pointed has two parallel
hexagon cut - A six-sided facetted cutting.
hexagonal system - One of the most important crystal systems, the
four axes of which are located as follows: three of equal length in one plane,
to each other; the fourth at right angles to this plane and longer or shorter
than the other three. Many gem minerals crystallize in this system and its
various classes, beryls, corundum and quartz among them.
hexagon tip - An item of jewelry findings; a hexagonal metal cup,
with a ring on its closed top for a necklace or other clasp; the cup to hold the
end of a chain or cord soldered or cemented in. See FINDINGS.
H.G.E. Abbreviation for heavy gold electroplate.
HI - Abbreviation for "heavily included." See CLARITY GRADE.
hiaqua - Necklace of strung shells or beads, of American Indian style.
hiddenite - (hidd'n-ite) A green variety of spodumene, found only in
North Carolina in small crystals, the coloring of which is caused by minor
amounts of chromium. It has not yet been shown that paler green spodumenes from
Brazil and Madagascar are colored by chromium and so entitled to this name, any
more than greenish beryl, colored by iron, can be called emerald.
high brass - Brass of high tensile strength, 66 per cent copper
and 34 per cent zinc, used for gear-wheels and other parts of watches and
clocks. See LOW BRASS.
high frequency - 1. Electricity. An alternating electric
current of high frequency, more than 20,000 cycles per second; a source of power
used in modern furnaces for efficient melting of metals. 2. Horology.
When referring to a balance watch, those beating faster than 8 times a second
(28,800 VPH or 4 Hz); the faster-moving train is less influenced by jolts,
gravity and poise errors, and may be regulated to close limits.
high relief - Ornamental work on jewelry, etc., in which designs
are formed standing well out from the background surface. See LOW RELIEF.
high speed steel - Steel
of great hardness and toughness containing a high percentage of tungsten,
retaining its cutting ability even when red hot; thus able to cut objects at
Hindu cut - Said by Schlossmacher to be the cutting form of the
Orloff, the principal requirement for which is that it should retain as much
size and weight as possible, without regard to symmetry requirements.
hinge-joint - One of the three or more pieces of metal tubing forming
with a pin a hinge for a watch case, locket, etc.
hinge pearls - Baroque pearls which grew near the hinge of the
mollusk; they are elongated and pointed at the ends.
Hinojosa topaz - Misnomer for citrine quartz from Hinojosa del
Duero, Cordova, Spain.
Hipp trainer - A device for closing a contact-making switch in
electric clocks of armature-driven pendulum type. A short, notched lever on the
pendulum trails across a knife-edge on switch; when the pendulum arc has been
shortened sufficiently, the notch catches on knife-edge, which is depressed to
close the switch and give a fresh electro-magnetic impulse to pendulum.
hobbing cutter - A spiral gear-cutter in the form of a continuous
thread used to cut gears and by its worm-like nature to rotate the gear blank as
it cuts, obviating the necessity of indexing.
hock - Also called Rhine wine, for the serving of which it is intended;
taller stemmed than the white wine or Port glass, and with a squatter bowl.
Capacity: 5 oz., sometimes 6 or 7 oz.
hoek - The first four top and bottom facets in diamond cutting, after the
table and culet are made.
hog-bristle regulator - An adjustable slide holding two stiff brushes
vertically, against which the foliot (balance-bar) of earliest watches banked,
to regulate its arcs of motion and produce a crude regulation of rate. From
this, probably, arose the current fable that the earliest hairsprings were hog
bristles bent into spiral form.
hole-closing punch - Steel punch with concave end, for reducing diameter
of pivot holes in brass clock or watch plates that have become enlarged through
hole jewel - The pierced jewel part of a cap-jeweled pivot
bearing, as distinguished from the unpierced cap-jewel (the end-stone) that is
set over the hole jewel to receive the end thrust of the pivot arbor. See
hole spar - Andalusite, variety chiastolite.
Holland rose or full Holland rose - A
rose cut stone with 24 triangular facets and a large single facet on the bottom.
Often attributed to Cardinal Mazarin, because he was the first to have any large
stones cut in this way. See DOUBLE HOLLAND ROSE; HALF HOLLAND ROSE; ROSE. Also
known interchangeably as Dutch rose.
hollow center - Required marking for a quality-marked article made
of karat gold, if the article has a hollow center that might deceive a
purchaser. Such an article may not be described as "solid." -From Rule 22, FTC
Rules for the Jewelry Industry.
hollow doublet - A doublet in which the lower side of the crown
portion or the top of the lower section has been hollowed out and filled with a
colored liquid. Rarely seen. See DOUBLET.
hollow fusee - Form of fusee with its upper pivot sunk in a
recess, designed to reduce the thickness of watch movements. See FUSEE.
hollow pearls - Misnomer for an early type of imitation pearl,
which consists of a hollow glass sphere, the inside of which is coated with the
pearl essence, and then filled with wax to give it weight and opacity.
hollow pinion - Pinion drilled through its entire length, as a
Swiss center pinion for a friction-fit setting-arbor.
hollow-rim balance - Form of chronometer balance invented by Victor
Kullberg, London, in 1885, with a pulley-like groove in outside of rim, to
reduce the middle temperature error in temperature adjustment.
hollow ring-ball - In item of jewelry findings, a hollow ball with
ring attached; used as a detail in assembling jewelry.
hollow-spindle lathe - Term used sometimes to differentiate live-center
lathe from dead-center lathe. See DEAD-CENTER LATHE; AMERICAN LATHE.
hollow wire - Tubular gold or gold-filled stock used for making
bracelets and other jewelry.
hololith ring - Term for a ring cut from a single piece of gem
material. Jade, quartz and jasper are often so cut.
homogeneous compensation - Correction for temperature effects on
tower clock pendulums, produced by a bar of metal that alters the position of a
fork embracing the suspension spring, to shorten or lengthen the acting length
of the pendulum by an amount equal to the changes in length of the pendulum rod
occasioned by heat or cold.
Honan jade - (ho-nan’) Same as Soochow jade, another misleading
name for soapstone or agalmatolite.
hone - A fine-grained natural stone (Ayrstone, bluestone, etc.) of slaty
character, used in the form of a flat-faced lap, with water, for leveling and
smoothing brass parts of timepieces preparatory to gilding.
honing - A modern process for finishing metal parts of machines, etc., in
which abrasive action is applied to the work in a variety of directions,
producing a surface super-smooth and accurately to form.
hood - 1. The part of the case of a long-case clock, or Dutch type
wall clock, that covers the movement; removable by sliding forward or upward,
for access to the movement. 2. A compartment with sliding, transparent
front and an effective exhaust for removal of dangerous gases when refining
hook, barrel - The slight extension on the inside of the barrel wall to
which the mainspring is hooked.
hooked graver - A hand-turning tool, its cutting part formed as a
projection to cut a seat in the barrel for the cover; or for cutting on the
bottom of the barrel without altering the mainspring hook, etc.
hook escapement - Common name for virgule escapement, developed to
its final form by J. A. Lepine, Paris, about 1780, as an improvement on the
cylinder escapement; it did not fulfill his hopes because of its inability to
retain oil on its acting parts.
Hooke's law - A principle in
mechanics discovered by Robert Hooke, basic to the action of hairsprings and
other springs in horology, which he stated in Latin: ut tensio sic vis ("as the
tension, so the force"); i.e., in an elastic material, strain is proportional to
stress; the value of stress at which a substance ceases to obey Hooke's law is
known as the elastic limit. See HOOKE, ROBERT.
hook-piece - English term for a
gathering pallet, that operates in connection with a rack in striking watches
and clocks. See HOUR RACK; HOUR SNAIL.
hoop - The ring part of a finger ring.
hoop wheel - In clock striking
work, a disc with a notch for a detent to stop the train at a position to allow
the warning pin wheel to make a portion of a turn before beginning the striking
of next hour.
Hope Star - Synthetic star
sapphire produced in many colors by Wiedes Carbidwerk in Freyung, West Germany.
It was introduced almost simultaneously with the Linde Star produced by the
Union Carbide Corp; its production continued after Union Carbide suspended
output of Linde Stars. See LINDE STAR.
Horatio diamond - Misnomer for
rock crystal from Arkansas.
horizontal escapement - The
cylinder escapement. "Horizontal" was applied as an early descriptive term,
because the escape wheel is in horizontal plane with movement plates, whereas
the earlier verge escape wheel is at a right angle or vertical to the plates;
the change of term from "horizontal" to "cylinder" came about gradually after
the verge or "vertical" escapement went out of use and when all escapements then
had horizontal escape wheels, requiring a new term to differentiate the
horizontal-cylinder escapement from the others. See CYLINDER ESCAPEMENT.
horizontal positions - In
adjusting watches to positions, the "dial-up" and "dial-down" positions of the
watch during timing.
horloge - (or'-loje’) French term for
any device that measures time; a clock.
horn - A gem shape, a thin curving
horn anvil - Anvil for
watchmakers' and jewelers' use, with a projection of pointed form to enter small
openings for riveting and forging operations.
hornblende - Loosely used for the
amphibole series, it is a member of that series, dark in color and without gem
use, See AMPHIBOLE.
horns - On the fork of a lever
escapement, projections on each side of the fork slot, for providing
safety-action during unlocking and impulse. See FORK.
hornstone - A fine-grained variety of quartz, named from the similarity
of appearance of some of the material to cow horn. It has a splintery fracture
and grades into chalcedony and jasper. In color it is gray, brown, yellow, green
or black. Schlossmacher includes apricotine and jasper as varieties. Today only
attractively-colored pieces are cut; these would now be called jasper, so it is
no longer of any gem significance.
Horological Institute of America - Organized in May 1921 by National
Research Council, Washington, D.C., to relieve the shortage of watchmakers and
award certificates of proficiency. Succeeded in 1960 by American Watchmakers
horologist - One who practices horology; especially, one who is learned
in theory and highly skilled in practice of horology.
horology - The science of time measurement, including the art of
designing and constructing timepieces.
Hot Springs diamond - Misnomer for rock crystal from Hot
hour angle - Angle, measured in hours, minutes and seconds of
time, which the declination circle of a star or planet makes with an observer's
meridian, at the celestial pole. See NAVIGATION; TIME DETERMINATION.
hourly controller - Mechanism for automatically setting a clock to
correct time every hour by an electrical impulse on a circuit wired to an
accurate clock at a central station. This system differs from master and
secondary clock systems in that the clocks controlled are each a self-driven
unit, instead of dependent for motion on current from central clock.
hour rack - In striking clock work, a toothed metal arc, one notch
of which is picked up by the gathering pallet for each hour struck. See HOUR
hour snail - In striking clock work, a disc on the hour-wheel, its
rim cut into 12 steps, to govern the number of strokes for each hour, by
stopping the tail-pin of the rack when the latter is released at each hour.
hour star - The star wheel upon which the snail of a striking
clock or watch is used to "flirt" and position the wheel into the next hourly
phase. Used when snail is not positioned directly on the hour wheel.
hour-wheel - The gear-wheel in the dial train of a timepiece which is
turned by the minute pinion, and on which is attached the hour hand.
hour-wheel pipe - A tubular extension on the hour wheel, surrounding the
cannon pinion, extending through the central hole in the dial, and carrying on
its outer end the hour hand of a timepiece.
hub - 1. The central part of a wheel. 2. Fixed arbor on
which winding wheel turns. 3. Arbor for the barrel in a motor barrel.
hulls - Thin nacreous layers of pearl.
humidity error - A slight slowing of rate in marine chronometers,
due to increase of moisture in air.
humper - Tweezers or pliers with jaws formed to bend guard-pin forward or
backward for adjusting guard-shake in lever escapement. See GUARD-SHAKE.
Hungarian cat's-eye - A greenish quartz with fibrous amphibole inclusions
from the Bavarian Fichtelgebirge.
Hungarian opal - Precious opal with a white, milky ground color
and lively small flecks of violet-blue, green and red. The Australian opal
production has displaced the Hungarian (Czechoslovakian) in the world market,
and little is now mined.
hunting case - A watch case on which the dial is covered by a lid
that may be thrown open by pressing a button on the pendant; differentiated from
open-face case, in which the dial is covered only by a glass or crystal.
hyacinth - (hi'a-sinth) Properly applied to orange, red and reddish-brown
zircon, also used not unjustifiably for yellow and brown zircon. Its use for
hessonite is erroneous and confusing, as are false hyacinth, oriental hyacinth,
and Ceylon hyacinth.
hyacinth of Compostella - Opaque, brick red, doubly
terminated quartz crystals from the gypsum beds of St. Jago of Compostella.
hyalite - (high'ah-lite) A clear colorless opal, also called water opal
or Mutter's glass. Of no gem significance.
hyalithe - A strong opaque glass resembling porcelain, in red, green,
black, brown, etc.
hydrocarbon - A liquid such as carbon tetra-chloride, tetrachlorethane,
or benzine, used as a degreaser.
hydrochloric acid - Also called muriatic acid. An aqueous solution
of hydrogen chloride gas, used in jewelry work and horology for many purposes. A
mixture of one part nitric acid and three to four parts hydrochloric acid
dissolves gold or platinum; hydrochloric acid is used for removing temper-colors
from steel, etc. See AQUA REGIA; TEMPERING.
hydrofluoric acid - An aqueous solution of hydrogen fluoride, used
for etching glass, enamel, etc.
hydrogen furnace - An atmosphere-free furnace in which the metal
heated is not subject to oxidation. This enables metals to be soldered without
the use of a flux and to emerge from the furnace clean and free of
hydrophane - (high'dro-fane) A variety of brownish, yellowish, or
greenish opal which absorbs large amounts of water and becomes almost
transparent. Upon drying out it again becomes opaque; the effect can be repeated
indefinitely. It is of gem interest only because of this property and little
used. Some reddish Mexican opal is of this type and is easily detectable because
of the way it clings to the tongue.
hydrostatic weighing - Determination of specific gravity of the
substance of an object by weighing it immersed in water, subtracting this weight
from its weight in air, then stating the specific gravity as the ratio between
(A) the weight in air, and (B) the difference found by the subtraction.
hydrothermal - Literally, high-temperature water; refers to the process
of stone synthesis by vapor (superheated steam) transport of material to a
growing crystal. Quartz crystals and Linde synthetic emeralds have been grown
commercially by the hydrothermal process. Other stones, rubies and zincite, can
be grown this way, but are more costly than those made by simpler methods. See
FLAME FUSION and FLUX FUSION.
hygrometer - Instrument for indicating amount of moisture in air;
sometimes used in astronomical clock vaults along with barometer, for
controlling atmospheric conditions affecting timekeeping of clocks.
hypersthene - (high'pers-theen) A variety of pyroxene, dark brown or
green to black. Sometimes showing a metallic schiller luster and cut cabochon
for collectors to give cat's-eyes, but of no real gem significance. See
hypocycloid - The path traced by a circle rolling within another. The
shapes of the flanks of pinion leaves in watches and clocks are de¬rived from
hypocycloids. See EPICYCLOID.
I - Abbreviation for "imperfect," "inclusions," or "included," in diamond
IC - Abbreviation for INTEGRATED CIRCUIT.
Iceland agate, Icelandic agate - Erroneous name for iridescent
gray or brown obsidian. See OBSIDIAN.
Iceland spar - Colorless, flawless calcite. Used in Nicol prisms
for polarizing microscopes and in dichroscopes. For many years a cave in Iceland
was the only source of this material, hence the name.
ice spar - A colorless sanidine and a confusing alternate name for
ichthyopthalmite - (ik-thee-ahf thai-mite) A fancy name for apophyllite,
the English equivalent, "fish eye stone," for this Greek root word having
already been used for other things.
icy flakes - Small internal cracks often present along twin
boundaries, but sometimes developed within a diamond by overheating on the
polishing lap. Icy is sometimes a term for a natural frosted surface on a
diamond, like artificially burned stones.
Idar agate - (ee'dar) An agate found near the German gem-cutting
center at Idar-Oberstein. This occurrence was the fundamental cause of the
growth of the industry at that spot. In general they are colorful but smaller
agates, not to be compared with the Brazilian-Uruguayan agates of today.
Idar-Oberstein - Gem-cutting center in the picturesque Nahe river valley,
southeast of Mainz, Germany. Several hundred plants polish, drill or engrave
colored stones; others cut diamonds. These skills originated with the cutting of
local agate, amethyst and jasper in the XVI Century.
I.D.B. act - The Illicit Diamond Buying Act, a South African law against
unlicensed trade in diamonds.
identification bracelet - Bracelet formed by a curved center plate
and flexible ends, the center plate being monogrammed or showing identity of
wearer; introduced in World War II.
idiochromatic - (id"ee-o-kro-mat'ic) Mineral coloration due to essential
elements of the composition of the mineral rather than to chance impurities; the
pigments of most gems. Turquoise and lazulite are examples of idiochromatic
gems. See ALLOCHROMATIC.
idle wheel - A wheel in a gear-train that does not affect the
ratio of turns, interposed to change direction of motion, or to accommodate a
distance of centers that would otherwise be wrong for the required ratio of
turns. See CENTER DISTANCE.
idocrase - (eye'doe-kraze) VESUVIANITE.
igneous rock - (igg'nee-us) One of the three great classes of
rocks, and the most fundamental of all. Igneous rocks are those which have
formed as the results of the solidification of a molten magma. Granite and
basalt, pegmatite dikes and diamond pipes are examples of igneous rocks and
formations. See SEDIMENTARY ROCKS; METAMORPHIC ROCKS.
illam - The sedimentary gravel deposits of Ceylon in which rubies and
sapphires are found.
illusion setting - A prong setting distinguished usually by a
narrow ring of metal surrounding the girdle of the diamond. The ring or rim is
provided to diffuse the sharp outline of the stone, thereby creating an illusion
that the stone is larger than it actually is.
ilmenite - A slightly magnetic, black iron titanium oxide, resembling
hematite, occasionally cut as a gem for collectors. It can be distinguished from
hematite by the brown streak it leaves upon an unglazed porcleain tile, in place
of hematite's red streak, and by its stronger response to a magnet.
imitation gem - A material resembling a gem-stone that does not
have both the composition and the structure of that gemstone. It usually refers
to glass, bakelite or other plastics which have compositions differing greatly
from the gems they simulate, but it is also used to describe natural stones so
treated as to simulate more-precious ones, e.g., German lapis (jasper dyed to
resemble lapis lazuli). Glass commonly used to imitate a diamond consists of 300
parts of quartz, 470 of red lead, 163 of potassium carbonate, 22 of borax and 1
of white arsenic; manganese, cobalt, copper, iron or chromium pigments are added
to simulate purple, blue, red, yellow-to-green, and green and red stones
respectively. Glass imitations have a hardness of 5 to 6; are singly refractive
and therefore do not show dichroism; have a refractive index of 1,50 to 1.80; a
specific gravity of 2.5 to 4.0; usually include air bubbles, and are warm to the
touch. See GLASS; RHINESTONE; BRILLIANT; CHATON; PASTE; STRASS; AVENTURINE; YAG.
Bakelite, a phenolformaldehyde plastic, is used to simulate both transparent and
opaque gemstones, but plastics are so different in physical and optical
properties from the stones they imitate that they can easily be detected.
imitation compensation balance - A mono-metallic balance
with rim half cut through from its top, used in cheap imported watches to
counterfeit the true bimetallic compensating balance. See BALANCE.
imitation diamonds - Currently, numerous materials not found in
Nature (and hence "synthetic" only in the broadest sense of the word) with high
refractive indices and, sometimes, strong dispersion. See YAG; STRONTIUM
imitation material - Horology. Replacement parts for repairing
watches, made by factories other than the manufacturers of watches in which the
parts are to be used.
imitation pearl - A manufactured product that simulates pearl.
Commonly, a transparent glass or plastic bead, thinly coated with synthetic
pearl essence. Better and more expensive, a translucent white glass bead,
thickly coated with essence d'orient, a solution of guanine from fish scales,
polished and lacquered.
immersion method - Stone testing, A method of refractive index
determination widely used among mineralogists, which essentially consists of
immersing the unknown substance, in index of refraction, until the liquid and
mineral are matched. See INDEX OF REFRACTION.
Imori stone - Imitation stones
made in all colors from devitrified glass, with some crystalline structure, by a
Japanese scientist. An imitation jade of this material is also called
impedence - The seeming resistance of a circuit in an electrical
timepiece to the flow of an alternating current.
imperfect - Abbreviated "I," the diamond clarity grade at the bottom of a
flawless-to-imperfect range. Stones of this grade contain inclusions and marks
that are visible without magnification to a trained eye. Sub-grades 11; 12 and
13 are used, according to the number, location and degree of faults.
imperfection - Gems. According to U.S. trade practice, any flaw, crack,
carbon spot, cloud or other blemish of any sort observable in a gemstone, when
the latter is examined by a trained eye under a 10-power magnifier. See
imperfection grade - See CLARITY GRADE.
imperial diamond - See GREAT WHITE DIAMOND.
imperial jade - A popular and trade term for the fine quality
translucent, emerald green jadeite. See also JEWEL JADE and PRECIOUS JADE.
imperial yu stone - See YU. This variety is prized by the
Chinese and is green aventurine quartz.
imperviousness - The ability of a watch case to withstand and exclude the
entry of moisture under pressure (water-resistance).
impression pad - A pad made of printers' gelatin, for quickly
making reproductions of an engraved design on pieces of work to be engraved to
match the original design. See TRANSFER PAD.
impulse - The act of applying power by an escapement to the balance of a
watch or to the pendulum of a clock. An impulse is given at every beat in lever
and cylinder escapements; at every other beat in chronometer-detent and duplex
escapements; at every beat in dead-beat and recoil verge clock escapements and
Riefler escapement; and at various longer intervals in other precision clocks.
impulse arc - The portion of the circular motion of a watch
balance during which the escapement is applying power to the balance; the
remaining amount of motion is the "supplementary" arc.
impulse clock - One of the dial-units of a master-and-secondary
clock system, in which the hands are moved, usually once a minute, by a ratchet
and click driven by an electromagnet and armature given an electric impulse
through a wired circuit from the master clock.
impulse face - 1. The inclined plane of the acting which
escape wheel teeth press to produce the "lift" in escapement action. 2.
The plane on the end of an escapement wheel tooth in club-tooth design of a
impulse pallet - In a chronometer detent escapement and in a
duplex escapement, the tablet of stone or steel attached to the balance arbor on
which the escape-wheel teeth press in applying power to the balance.
impulse roller - In the double-roller lever escapement, the disc
on the balance staff in which is set the roller-jewel to which power is applied
by the fork, and thus through the impulse roller is power applied at each
vibration of the balance to keep it going. The other roller in a double-roller
escapement is the safety or guard roller. See LEVER ESCAPEMENT.
impulse spring - A suspension
spring for the pendulum of precision clocks of the Riefler type, through which
escapement impulses are imparted to the pendulum; the cradle to which the spring
is fastened is rocked by a crutch attached to the pallets, this motion bending
the spring sufficiently to maintain the momentum of the pendulum.
impulse tooth - In a duplex escapement, one of the vertical teeth
on the web of the escape wheel that act on the impulse pallet, differentiated
from the horizontal teeth that rest on the balance staff to provide locking
in beat - The condition in a lever watch in which the hairspring,
at rest, with no power on the escapement from the train, will bring the balance
to a stop with the roller jewel standing exactly above the line of centers of
the escapement, with the fork-lever in the center of space between the bankings;
in a cylinder escapement, when in beat, the acting ends of the cylinder lips
both lie on a line intersecting the escapement's line of centers at right
angles. A pendulum clock is in beat when the impulse is applied at equal angular
distance on each side of the center of its arc of motion. An out-of-beat
condition in a watch or clock is indicated by hearing it ticking at intervals
alternately long and short, instead of in periods of equal length.
incise - To cut into or engrave so that a sunken line is produced.
incised - A term applied to the lines produced by a burin or graver.
inclination test - Taking the timekeeping rates of marine
chronometers, with the instruments running in positions at an angle from the
normal horizontal position of the dial which would normally be maintained by
action of the gimbals; the gimbals are locked out of action during an
incline - The acting edge of a tooth of an escape wheel in a cylinder
incline plane clock - An unpowered drum clock rolling
slowly down an inclined plane. An inside counterweight acting on the train of
gears supplies the restraining as well as motivating force.
inclusion - 1. Crystallography. Any evidence of interruption in
crystal growth, including (a) protogenic, or pre-existing, inclusions-foreign
solid matter or guest mineral present before the gemstone crystallized and
trapped it; (b) syngenetic, or contemporary, inclusions, formed simultaneously
with the gemstone— foreign minerals, drops of mother liquid, or gas bubbles that
were encased within the growing crystal; (c) epigenetic, or subsequent,
inclusions, occurring after the gemstone was formed—due to re-crystallization or
penetration of outside substances along cracks and fissures.—After Dr. E.
Gubelin. 2. Diamond grading. Inclusions, also called "internal
characteristics," for which polished diamonds are examined in clarity grading,
include: cleavages, fractures, knots, bubbles, carbon spots, clouds, fezels, and
bearded or feathered girdle.
inconel - A white gold imitation alloy.
incrustation - Decorative work
consisting of the inlaying of ornamental material such as precious metals or
stones in the surface of the article incrusted.
independent seconds - A type of chronograph in which the seconds
hand is driven by a separate gear-train instead of by the regular time-train.
index pin - 1. On a watchmaker's lathe, a thrust-pin
engaging with the circle of holes on the back of a driving pulley, for dividing
work into faces of holes to be filed, milled or drilled in definite angular
relation to each other. 2. One of the pair of pins that embraces the
outer terminal coil of a hairspring and connects it with the regulator.
index, regulator - The arm or hand of regulator of a watch, that moves
over a graduated scale usually on top of the balance cock to judge the amount of
Indian agate - Moss agate.
Indian jewelry - Jewelry, characteristically silver set with
turquoise, made by Indian residents of the United States. Members of the Navajo
and Zuni tribes learned the art between 1850 and 1870 from Mexican blacksmiths
and silversmiths of the Rio Grande valley, and soon were making bracelets,
rings, necklaces, pins, hair and belt ornaments and other jewelry. Non-Indian
manufacture of such jewelry began in 1910. Such jewelry not made by Indians may
be called "Indian type," "Indian style," "Indian look" if the word "Indian" or
designs associated with Indians are used in its promotion. See HAND-MADE.
Indian cat's-eye - Chrysoberyl cat's-eye.
Indian cut - A term for asymmetrically shaped gems, cut in India
and Sri Lanka, designed to yield the maximum return (in weight) for the piece of
rough. Most stones so imported are recut for Western tastes. All the standard
cutting forms, such as brilliant, step, mixed and cabochon, are recognizable in
these distorted native-cut gems.
Indian emerald - Misnomer for crackled green quartz.
Indian garnet - Almandine.
Indian jade - A misleading name sometimes applied to aventurine
Indian topaz - A name of many meanings, at best, a saffron yellow
topaz, typical of the Ceylon gravel deposits, and at worst, citrine quartz, with
yellow sapphire between the two extremes. See BRAZILIAN TOPAZ; KING TOPAZ.
Indian pearl - Oriental pearl.
India oilstone - Abrasive material manufactured in forms like
laps, slips, wheels, etc., for grinding tools, shaping timepiece parts, etc.; a
durable and fast-cutting material for the purpose.
indicator. - 1. A trueness-testing instrument for chucks or work
in a lathe, with leverage mechanism for magnifying errors. 2. The hand on
the setting-dial of an alarm clock.
indicator, winding - A device on precision watches and chronometers with
pointer on dial to show the extent to which a mainspring is run down, to insure
against forgetting winding the timepiece,,
indicolite - Light or dark blue tourmaline, one of the rarer colors of
the gem. Also known as Brazilian sapphire.
indigo sapphire - Very dark blue sapphire. See WATER SAPPHIRE.
indirect seconds - A center seconds hand not connected directly to
the fourth wheel (which is not situated in the center of the watch). See DIRECT
inductance - The initial opposition of a conductor to a current.
induction motor - Type of alternating current motor used in
electric clocks in which current in a primary winding induces current in rotor
to produce rotation.
industrial diamonds - Diamonds usually unsuitable for gem
purposes, because of flaws or poor color, and which are, therefore, used in
industry because of their superior hardness over all other materials. Between 75
and 80% of all diamonds mined are so flawed or poorly colored that they are fit
only for industry. Diamond saws, diamond drills and wiredrawing dies are among
the uses to which such stones are put. BALLAS, CARBONADO and BORT are all
industrial grades of diamond.
infrasonics - Below the perception of human hearing, in contrast to
ingot mold - A mold, which, for jewelry work, is usually made of
iron and with adjustable walls, to produce a variety of sizes of cast metal bars
or ingots. The side walls are detachable, to facilitate removal of the ingot
from the mold.
initial ring - A finger ring, worn mostly by men, with the initial
letter of the wearer's name made of metal set on a background of stone or gold
of contrasting color.
ink-recorder - A form of chronograph or timer watch which makes an inked
dot on a dial to record the time at which the hand is stopped.
inlay - 1. Type of decorative work used on wood clock cases, etc.,
in which thin, flat material, cut into a design, is sunk in a counterpart of the
design cut in the surface of the article. Contrasting colors of metals, woods,
ivory, etc., are used. 2. In jewelry, to embed a material in another
substance so that the surfaces of each are level. Stones may be inlaid in metal,
as can metals of contrasting colors.
inner-terminal hairspring - A balance spring of the Breguet or
over-coiled type, which has also a definitely formed terminal curve in the coil
nearest the hairspring collet, designed to work with the overcoil in improving
the isochronal and position timekeeping rates of a watch. See CURVES; TERMINAL;
inoxidizable - The ability to withstand rust or tarnish such as stainless
steel, gold, etc.
insert guard ring - A double ring, sometimes ornamented
with gems, with a space between to accommodate another ring in its center.
Together, they appear as one larger ring.
inside drop shake - In a lever escapement, the movement of
the escape wheel during the time after a tooth has become disconnected from the
lifting plane of the receiving pallet, until another tooth has come into contact
with the locking-face of the let-off pallet See DROP.
inside graver - Engravers' graver with bayonet-shaped or S-curved
end, for cutting lettering inside of finger-rings, deep bowls, etc.
insulator - Horology. An outer-case made of soft iron lined with velvet
or leather, enclosing a watch being worn, to protect it from magnetisation.
Action is that magnetic currents flow through the iron insulator around the
watch instead of through it. Silversmithing. Small pieces of heat-resisting
substances (usually ivory) inserted in the handles of coffee and teapots to
prevent the handles from becoming hot.
intaglio - 1. A form of work for decorative or other uses, in
which a design is cut below a surface which forms the background for the design.
2. An engraved gem, of which the rim is the highest portion and the
figure incised below it, either as a negative impression or raised above a
depression in the center, and thus resembling a cameo. Coats of arms and
monograms, subjects suitable for a seal, are common carvings in an intaglio, as
well as the figures usually seen in cameos. See CAMEO.
integral balance - A balance for chronometers and precision
watches, invented by Charles Ed. Guillaume of Sevres, France, with a bimetallic
rim of brass and nickel-steel, which eliminates the middle temperature error.
See MIDDLE TEMPERATURE ERROR.
integrated circuit - An electronic circuit made with
semiconductors, used in solid state watches as a frequency divider, reducing the
frequencies put out by the quartz crystal or other frequency standard. In solid
state digital watches, it also decodes the time information, provides
memory-recall services, and drives the display and other parts of the timepiece.
intermediate wheel - See IDLE WHEEL; INTERCHANGE WHEEL.
interference colors - Hues given off by a bire-fringent substance
under examination, between crossed polarizing devices, in a polariscope or a
petrographic microscope. Running the spectrum from gray to red and blue, the
hues are caused by one ray being slowed more than another as they reunite after
passing through the specimen into the second polarizer. Their hue and intensity
may be used to judge the relative strength of birefringence; bright colors are
referred to as first order colors; those slightly less intense as second order
colors, and so on. If a stone is so highly doubly refractive that there is no
hue, a polariscope or card test can determine whether it is doubly or singly
refractive. See BIREFRINGENCE.
interference figure - A phenomenon observed in convergent
polarized light with crossed nicols. Figures are useful in the determination of
the optical character of unknown gems, and are fairly constant properties of any
internal gearing - Gear wheel with teeth inside its circumference,
pointing toward the center, as in the escapement carriage of a tourbillion or
karrusel watch. See KARRUSEL; TOUR-BILLON.
internally flawless - A clarity grade for cut diamonds that came
into use during the early Nineteen Sixties; sometimes abbreviated "IF." A
diamond can only be defined as internally flawless when, examined by an
experienced professional under 10-power magnification in normal light by means
of an achromatic, aplanatic lens, it proves to be absolutely transparent and
free from inclusions or internal characteristics—CIBJO. A diamond which has no
internal characteristics but which, due to minor finish faults is not "flawless"
and therefore cannot be designated FL or "flawless," may be called IF or
"internally flawless" provided the finish faults are so minute that they can be
removed by a gentle polishing with an insignificant loss of weight only -
Scandinavian Diamond Nomenclature.
internal stress - Gemology. Stress resulting from inclusions or
other structural irregularities, visible, in singly refracting stones, like
diamond, through the polariscope.
international lathe - A type of watchmaker's lathe, with the bed
made of a round bar milled flat on back side to keep attachments upright; a
European modification of American-type lathe, designed to reduce manufacturing
Interrupter - In electrical horology, a form of current breaker or
interval clock - A precision clock for laboratory or
manufacturing-process use, with buzzer or bell to signal elapsed time periods,
for taking data in chemical or other experiments or operations.
intrados - The convex underside of an arch, as that of a clock case.
intumescence - (in'too-mess"sense) Fusing accompanied by bubbling, the
result of some component escaping as a gas. Many gems melt in this way, though
high temperatures are necessary to fuse them at all.
invar - An alloy of nickel 36 per cent and iron 64 per cent, which has a
very low coefficient of expansion; used in horology for precision clock pendulum
rods and integral watch balances.
inverted pendulum - A slow-moving, short pendulum effected by
placing almost half its mass above the point of suspension such as used in
metronomes and swinging ball clocks.
investing flask - Stainless steel tubes of different sizes used to
hold investment molds for casting.
investment - A refractory material used to surround a disposable pattern,
as of wax, and act as a mold for receiving metal which fills the cavities of the
iolanthite - (eye'o-lanth"ite) Local name for a banded reddish jasper
found in pebbles in gravels of the Crooked River, in central Oregon.
iolite - (eye'o-lite) A magnesium, iron, aluminum silicate mineral which
is sometimes used as a gem. It is interesting for its strong pleochroism; in the
three pinacoidal directions it shows deep blue, light blue-gray, and
yellow-white, respectively. Cut gems will usually show some of this pleochroism
to the naked eye. Its hardness is about that of quartz, its specific gravity
2.6, and its refractive index about 1.55. It is found in a number of places,
usually in metamorphic rocks, but only rarely is it possible to cut gems of more
than a few carats. Also known as CORDIERITE and DICHROITE.
Ionic - Term designating one of the three orders of Greek architecture,
distinguished by the spiral scroll-shaped ornaments of its capital. Candlesticks
are often made in this style.
ionization - A process in which particles of a gas become carriers of
electricity. The transformation of an atom into a positive or negative ion.
Iran lapis - Persian lapis.
Iran turquoise - Persian turquoise.
iridium - A hard white metallic element of the platinum group, the most
corrosion-resistant and possibly the densest element known. In the massive form
it is unaffected by all acids, including aqua regia. Melting point, about
2454°C.; specific gravity 22.4 to 22.6; chemical symbol Ir. Its main use is as a
hardener for platinum, the alloys being used in jewelry, dentistry, electrical
contacts, chemical equipment, pen points-, etc. The platinum alloy containing 10
per cent iridium, preferred for high-grade jewelry, is known as "hard platinum;"
the 5 per cent alloy as "medium hard platinum." See also PLATINUM GROUP.
iridosmine - (irr'i-doz"min) A naturally occurring alloy of osmium and
iridium, also called iridosmium and osmiridium. The hard grains are used for
tipping pen points and phonograph needles. See OSMIRIDIUM.
iris - Rock crystal containing thin cracks which show iridescent
coloring. This type of material was formerly popular for gem use, and it is
possible that some of the "opals" of the ancients were really this iris or
iris agate - A type of banded agate which, when cut into a thin
slice and polished on both sides, shows an iridescent band when held up toward a
strong light source. It is caused by refraction from innumerable microscopic
crystals of quartz in certain layers in the agate; a coarser banding does not
create the rainbow effect. As the agate must be sliced very thin, it has not
found much gem use, most slices being mounted in cardboard so that the
phenomenon may be observed at its best with the surrounding light shut off. Also
known as RAINBOW AGATE.
iris diamond - According to Schlossmacher, a misnomer for a novel
trick of coloring the lower facets of a diamond to give an imitation of strong
dispersion and great fire.
Irish diamond - Misnomer for rock crystal.
Irish pearl - A natural fresh water pearl from the ancient
fisheries at Omagh, Ireland.
iron core coil - An electromagnetic coil wound around a
soft iron core.
iron glance - Hematite.
iron lap - A grinding lap made of malleable iron, used mostly with
pulverized oilstone in oil as an abrasive for shaping and finishing steel parts
of timepieces. Iron laps are made in forms of hand-slips for pivot and staff
work, wheels for same purposes used on rotary pivot polishers, and flat
benchlaps of large area for flat steel work.
iron opal - A weakly translucent brown, red, yellow or greenish
variety of common opal. Also called JASPOPAL or OPAL JASPER.
iron oxide - Ferric oxide; iron rust; pulverized, washed and
decanted, it is the rouge used for polishing jewelry, metal watch parts, etc.
iron pyrites - (py-rye'teez) A popular misuse and mispronunciation
of the term pyrite. Though sanctioned by dictionaries, iron pyrites is never
used by mineralogists.
ironstone china - A type of hard earthenware patented in 1813 by
Charles Mason, supposedly having iron slag as one of its constituents. See
STONE, CHIN A.
irradiation - A method of treatment to effect a change in a gemstone's
color involving the use of sub-atomic particles, x-rays, gamma rays, neutrons,
deuterons or electrons. Successful in the more or less permanent coloration of
diamond (brown, yellow, blue, green, black), beryl (green, golden), topaz
(blue), tourmaline (pink, red, purple, yellow), quartz (smoky, amethyst). See
RADIUM TREATMENT; PILE-TREATED STONES.
irregulars - A diamond shape classification, crystals of irregular shape
with broken parts. Comes after "goods" and before "cleavage."
isolator - (eye"so-lay'tor) Mechanism in a minute repeater for preventing
contact of the click and the surprise piece until operation of the finger-slide
on the case has been completed.
isometric system - (eye'so-met"ric) The preferred name of the
cubic system of crystallization. Substances which crystallize in this system are
isotropic and their crystallographic axes are all of equal length; hence the
name, from "equal" and "measure." See CUBIC SYSTEM.
isomorphous replacement - (eye'so-mor"-fuss) The replacement,
chemically, of one element by another, without any disruptive change in most of
the properties of the compound. Iron and magnesium, for example, replace each
other isomorphously in the olivine series of minerals, and chromium probably
replaces aluminum isomorphously in ruby.
isopropyl alcohol - A colorless inflammable liquid used by
watchmakers for drying as well as dissolving shellac.
isotropic - (eye'so-trop"ic) Not birefringent, light passes through an
isotropic substance in all directions at the same speed. Isometric minerals,
glass and other amorphous substances are isotropic. See ANISOTROPIC.
Isobval - A whitish alloy used in hairsprings claimed to improve
Italian chrysolite - Vesuvianite.
ivory - The hard creamy white, opaque substance of which the tusks of
elephants are composed, or, more generally, the teeth of any animal; walrus
ivory, for example, is often used in decorative objects.
ivory clasp - A type of necklace cord end-fastener, consisting of
two short barrels, attachable by a male and female screw, used for necklaces of
beads other than metal beads.