jacinth - (ja-sinth) Reddish brown zircon, also known as hyacinth. Sometimes
used, but confusingly, for grossular garnet of this color.
Jacobs chuck - An adjustable chuck with three jaws used in drill presses and
adaptable for lathework.
Jacot lathe - A special-purpose watchmakers' lathe, in which work is supported
on dead centers and driven by a hand-bow, used for polishing watch pivots with
hand-laps, to give them finish or to alter their form in adjusting See BOW
LATHE; DEAD-CENTER LATHE.
jacut - Persian term for sapphire, and the root of our word, jacinth.
jade - A collective name which includes two minerals, nephrite and jadeite, of
which the latter is the rarer and more valuable species. It is fundamental that
the crystal structure be "felted"; i.e., not parallel but interlocking. Only
then do we have a texture and toughness that makes jadeite and more especially
nephrite, truly jade. Parallel fibred nephrite is known, cat's-eye cabochons can
be cut of it, but it cannot be regarded as jade when it has this structure, for
it lacks the toughness of jade. Many other materials are carved by the Chinese,
and many other materials are green and tough like jade, but none is properly
called jade, other than these two. The colors have received various names in
China as Hsi (white), Pi (blue), Lu (feather green), Kan (color of boiled
chestnuts), Man (like veins filled with blood), Hsieh (black), Ch'a (fatty
flesh), Juan (red and white). Buried jades are called Kan Huang (stained
yellow), Lao Kan Huang (deeper yellow), Kzu Ch'ing (stained blue), Loa Kan
Ch'ing (deeper blue), Hai Erh Mien (red with ashes), Chuen Ch'i Hsi (black from
mercury), Tsao P'i Heng (date skin red with blood); imitation jade colors: Lao
Ti Yu (chicken blood red, from an herb, a rare and ancient dye), Hsiu Ti Yu
(colored by burning in a colored box); and ancient jades; Lao San Tai (soft
excavated pieces). Names from Goette, "Jade Lore." See NEPHRITE, JADEITE,
jadeite - (jade'ite) A sodium aluminum silicate containing some calcium
magnesium silicate (a considerable amount in the case of the Mexican jade) and
a member of the pyroxene group of minerals. The best comes from Upper Burma,
where it is often found as boulders of hard, compact fibers; it is this
structure which gives the jadeite its toughness, even though its hardness is not
remarkable. Cavities with single, large transparent crystals are not known, the
coarsest crystals seem to be those of the long-sought Mexican occurrence.
Grayish, small, idiomorphic crystals have been found in California, but the
occurrence has no economic value. Jadeite comes in many colors, of which white
and whitish is the commonest; in all shades and tints of gray, orange-red,
mauve, black, and green. The greens are the most valued and range up to a
brilliant emerald hue, which, when uniform and fairly translucent, is very
highly prized and goes under the name jewel jade. Its hardness is 6 to 7, its
density about 3.3. See also AMPHIBOLE.
jadeolite - Misnomer for a deep green syenite resembling jade in appearance and
coming from the Burma jadeite locality.
jager - (yah'ger) A diamond quality name, originally applied to certain fine
diamonds coming from the Jagersfontein Mine, their slightly bluish color
resulting from strong blue fluorescence; the highest grade in the traditional
jahalom - A stone in the breastplate of the High Priest of the Jews, long
believed to have been diamond; now thought to have been corundum; derived from
halom, "to beat" or "to overcome."
jam-nut - A screw-nut used with another nut to tighten it after adjustment, as
on a pendulum-bob regulator.
Japanese coral - Coral from Japan, the most common variety of which is dark red
with a white core.
Japan pearl - An older, trade misnomer for the early cultured "half pearls"
developed by Mikimoto before the spherical modern cultured pearls. See MABE.
jargoon or jargon - Name sometimes applied to white zircons offered as diamond
substitutes. It has also been used for yellowish, off-color diamonds.
jaseron chain - A fine gold chain worn in the 19th Century, with crosses,
pendants and mosaics.
jasper - 1. A fine-grained, impure, massive quartz aggregate, characterized by a
lack of any regularity of orientation of the microscopic quartz crystals and by
its complete opacity. It has a smooth, conchoidal to uneven and angular fracture
and a dull to greasy luster on the fracture face. Usually it is strongly
colored. The differentiation from agate and chalcedony by cutters is based upon
the transmission of light — when the stone is completely opaque, even on thin
edges they call it jasper; if translucent, even slightly, it is called
chalcedony; and if translucent and brightly colored, agate. See also ADINOL;
BANDED JASPER; BLOODSTONE; BLOOD JASPER; BOAKITE; BIRD'S EYE; QUARTZ; CATALINITE;
CHERT; CREOLITE; HELIOTROPE, etc. 2. Stoneware. A hard, dense stoneware
developed in 1775 by Josiah Wedgwood; body colors, often with the well-known
white relief, included black, yellow, green, blue and lilac.
jasperine - Banded jasper of varying colors.
jasper jade - Misnomer for green jasper.
jasper lap - A polishing lap used in watchwork, made of natural stone of opaque
impure silica, usually red in color. Jasper laps are made of flat form and
considerable area, for polishing jewel settings by hand-rubbing; or in the form
of long thin slips mounted in handles for polishing pivots on a lathe.
jaspilite - (jass'pi-lite) Banded hematite and jasper.
jaspis - Ancient name for chalcedony.
jasponyx - (jass'po-nix) An opaque material with the banding of an agate, but
grading into a jasper.
jasp opal - Intermediate stage between jasper and opal.
jet - A black, compact variety of the brown coal, lignite, which takes a fine,
velvety polish. It is soft 3-4 on the Mohs scale and light in weight (1.30-1.35
s.g.); like any other coal, it will burn. Popular in the middle of the last
century, it is little used today, its place being taken by harder stones, like
onyx and black tourmaline. Chief source, Whitby, England.
Jet Black - A commercial solution which coats gold with a black coating. May be
applied by heat or by electroplating.
jet glass - A black glass made to imitate jet. Harder than true jet, it will not
burn and is not marked by a hot needle.
jet stone - Black tourmaline, though it is rarely used, as other substitutes are
jewel - 1. A stone or other substance, as pearl or amber, cut, polished or
otherwise prepared for use or beauty. 2. An ornament, usually for personal wear,
made of precious metal or an imitation of precious metal and often set with
gems. 3. A bearing for a pivot in a watch or other precision instrument, formed
of corundum, garnet, glass, etc.
jewel bezel cutters - Sets of steel bits used in lathe chuck or hand-drill for
forming seat and bezel for setting watch jewels directly into place or bridge.
jeweler - 1. A merchant who sells diamonds, other gemstones and jewelry, as well
usually as watches and clocks and, often, silverware, china, crystal, giftwares
and other merchandise. 2. One who makes or repairs jewelry, as distinguished
from such other craftsmen as watchmakers or engravers.
Jewelers Board of Trade - A credit-rating and collection agency of Providence,
R.I., founded in 1874; supported by 1300 manufacturers, wholesalers and
importers; publishes a semiannual Confidential Reference Book and a weekly
Jewelers Security Alliance of the United
States - A non-profit crime-prevention
association of retail, wholesale and manufacturing jewelers; founded in 1883;
pays reward for arrest and conviction of individuals committing crimes against
members; helps members in crime-prevention.
Jewelers Vigilance Committee - Sometimes defined as "the conscience of the
industry;" incorporated in 1917 "to investigate complaints of violations of
stamping, misbranding, false advertising and similar laws ... To keep in touch
with members of the jewelry trade in all parts of the United States, with a view
to cooperate with such members and other bodies, in the enactment of needed
legislation ... to the end that in time such laws shall be uniform and
efficacious in all parts of our country."
jewelers' lathe - A lathe for polishing work with rotary buffs, comprising a
spindle and pulley in bearings on a simple bench mounting, differentiated from
the watchmakers' lathe or other lathes used for turning. See LATHE.
jeweling caliper rest - An attachment for an American-type watchmakers' lathe,
for automatically measuring diameters of jewels to be set, and mechanically
transferring the measurement while cutting seat for jewel in a blank for
jeweling chuck - Special split wire chuck for holding jewel settings during
recessing, burnishing, or stripping operations; one form is an assortment of
split chucks small enough to hold in a large size lathe chuck; another is an
assortment of regular lathe chucks with recesses countersunk on face around
hole, of various diameters to hold jewel settings.
jewel hole gauge - A tapered steel pin, mounted to slide in a handle with
graduated scale, with an index on the pin that indicates on a scale the diameter
of hole in a watch jewel.
jewel pin - See ROLLER JEWEL.
jewel-pin setter - A device for holding and applying heat to the roller table of
a lever escapement, to soften cement while replacing or resetting a roller
jewel pusher - Set of punches of assorted sizes, made of soft metal, for
removing jewels from watch plates and bridges.
jewelry - Articles of personal adornment such as rings, bracelets and necklaces,
made of precious or non-precious materials, often set with natural, synthetic or
imitation stones or natural, cultured or imitation pearls.
jewel-screw countersinks - Sets of small flat-bottom recessing mills with
centering pins, for cutting sinks intersecting a watch plate and jewel setting,
to hold screws fastening setting to plate.
jewel setting - 1. A metal ring in which a hole or cap jewel is set by
burnishing the corner of the jewel seat over the edge of jewel, the outer edge
of the setting then being turned to fit a recess in a plate, bridge or cock of a
watch or clock. 2. The operation of setting jewels. See JEWELING.
jewel tweezer - A tweezer with a device for locking its jaws in place to hold
watch jewels without slipping; with recesses in the jaw tips, used while
cleaning gems to avoid risk of losing them.
jigger - A bar accessory measuring cup, usually of 2 oz. capacity; when made as
two cups, base to base, the second cup has 1-oz. capacity.
jobber - A term now generally regarded as archaic and in disrepute for
jobbing stones - A jeweler's assortment of unmounted stones, kept for use in
job shop - Term used in the watch and jewelry trade to designate a "trade shop"
that does repairing, as distinct from a shop where goods are manufactured.
Job's tears - Small pebbles of chrysolite or peridot, from Arizona and New
johnite - Vitreous or scaly turquoise occurring in siliceous schists, named
after J. F. John who (in 1806) had furnished the best analysis of that mineral
to date. See also TURQUOISE; AGAPHITE; CALLAITE.
joint - 1. An item of jewelry findings, soldered or screwed to a piece of
jewelry, to form, with a pin, a hinge for the pin with which the piece is
fastened to clothing of wearer. 2. A hinge formed by three or more sections of
tubing. See JOINT WIRE.
joint buff - A hard felt buff of lenticular form, for use on a jeweler's lathe,
for polishing in crevices or grooves.
jointer - A hand-driven milling tool, for cutting parallel sides on a joint to
prepare for soldering in resizing or repairing finger rings.
joint file - A file with flat parallel uncut sides and rounded edges cut with
teeth, to produce grooves into which the joints or knuckles of a hinge are
soldered, for watch cases, lockets, etc.
joint fork - A large fork with two long tines, used to hold a roast of meat in
position while carving.
joint pin - The metal pin fitted friction-tight in holes in end-joints of hinges
of watchcases, etc., on which the lid-joint of a case, or a pin-base turns as a
joint pin pusher - Steel punch, used in sets of assorted sizes, for removing
hinge pins of watch cases and jewelry.
joint tool - A device for cutting tubing and filing the ends square. The tubing,
placed in the triangular opening and held in position by its set-screw, is cut
or filed against the hardened surface of the tool.
joint wire - Hollow wire or tubing formed by bending a strip of thin, flat plate
and drawing it through a drawplate until the desired diameter and opening are
obtained In making seamless tubing, a disc of metal of appropriate thickness is
successively punched to cup shape and drawn to desired size. Used to make hinges
for watch cases, lockets, etc.
Jolly balance - An instrument used for the determination of specific gravities
of minerals. It consists of a slender spiral spring suspended from a standard on
which a scale is marked and supporting a pan or pair of pans with which the
weights of the stone in question can be determined for both air and water. It is
named for its inventor, P. von Jolly, a German physicist.
journeyman - A workman who has completed learning his trade, and is fit to hold
a job as a full-fledged workman, as a journeyman watchmaker or jeweler; to
differentiate from an apprentice, student, or other workman who cannot do all
jubilee cut - A modified brilliant cut named in commemoration of the sixtieth
anniversary of Queen Victoria's accession in 1897. In it the table and culet are
replaced by extended star facets and other modifications are made in the other
facets, making a total of 88 facets.
jug - A deep plain vessel of china or silver for holding liquids. It usually has
a handle, flat base, circular body and small lip.
jump-figure dial - A timepiece dial mechanism in which the numerals are on
disks, moved usually each minute by a pawl and ratchet, and appearing in a small
opening in the dial-plate to indicate time. Some timepieces have hours only
shown in this way; others, hours and minutes. See RATCHET.
jump ring. An item of jewelry findings; plain rings of graded sizes and various
metals, round or oval, the ends of wire meeting but not soldered together, for
attaching parts of jewelry together, in manufacturing assembling, or repairing.
K, Kt - Abbreviations for karat.
kahurangi - A pale-green translucent variety of New Zealand nephrite jade.
Kalmuck agate, opal - See CACHOLONG. The name is probably derived from an
occurrence on the Cach river, in Bokhara, central Asia.
Kandy spinel - False name under which Ceylonese almandite garnet is sometimes
kaolin - A fine white clay consisting of decomposed feldspar, a non-fusible
silicate of aluminum; a component of porcelain. Also called china clay.
kaolite - Name given in Arizona to molded stones of various colors, made in
imitation of Indian carvings, cameos, etc., for use in costume jewelry.
Presumably a baked clay, the name is from that of the principal clay mineral,
karat - One twenty-fourth part by weight of the metallic element gold in an
alloy. Pure or fine gold is 24 karats; 18 karat gold (abbreviated 18 K. or 18
Kt.) consists of 18 parts of pure gold, mixed with 6 parts of other metal; 14
karat gold (abbreviated 14 K. or 14 Kt.) is 14 parts of pure gold, combined with
10 parts of other metal; etc. Together with carat, which see, the word is
probably derived from the Greek, kemtion, signifying a seed used in ancient
times for weighing pearls. Its connotation of l/24th, as applied to gold, stems
from the weight of the solidus, a gold coin used in Byzantium from 312 A.D. to
1453 A.D. By law, the solidus weighed 4 scruples, each of which was equal to 6
kerations; thus, the solidus weighed 24 kerations or karats. In England, the
spellings "caract" and "carrott" were used as late as the 17th Century,
superseded by "carat," which is still used outside the United States with the
same spelling to denote both the ratio of fine gold in an alloy and the unit of
weight for gemstones. In U.S. usage karat designates the proportion of fine gold
in an alloy; while carat is applied to the weight of a stone. See CAROB; CARAT;
Karat Clad - A registered trade name for heavy gold electroplate, meeting
Federal Trade Commission regulations for gold coating at least 100 microinches
thick. See HEAVY GOLD ELECTROPLATE.
karat gold - A gold alloy of not less than 10 karat fineness, preceded by the
karat fineness of the alloy, such as 14 karat gold or 14 K. gold. Fineness may
also be designated without the word gold, such as 14 Karat or 14 K.—From Rule
22, U.S. Federal Trade Commission Rules for the Jewelry Industry. The International Confederation of Jewelry, Silverware, Diamonds, Pearls and Stones
(CIBJO) favors two standards of gold for international commerce: 18K and 14K.
See TOLERANCE; PLUMB GOLD; NATIONAL STAMPING ACT.
karat needles - A set of brass tongues hinged on a handle, tipped with various
karat-grades of gold, used with test stone and acid to determine the fineness
of a gold object. See TOUCH-
STONE; ACID TEST.
karfunkel - The ancient indefinite name of Indian legends for a red stone; in
the Middle Ages "karfunkel stones" were principally garnets,
Karlsbad Spring stone - A banded red, white and brown gypsum used in small
carved objects and cheap jewelry.
karrusel - (kar'oo-zell") Arrangement of the connection of train with
escapement in a watch, in which the entire escapement and balance is in a
framework pivoted so that it keeps turning to all the vertical positions as the
watch runs, more or less eliminating position errors of time-keeping. This is a
variety of "tour-billon" construction, invented by B. Bonniksen, of Coventry,
England, in 1902. See TOURBILLON.
Kashan synthetic ruby - Synthetic, flux-fusion ruby made in Dallas, Tex., by Dr. Trueheart Brown.
Kashmir sapphire - Theoretically, cornflower blue sapphires from the Zanskar
range of the northwestern Himalayas in Kashmir, but, as generally used in the
trade, the name for any sapphire of this fine quality. They are characterized
by a slight velvety look (cloudiness) and fine blue hue in all lights and are
considered the ultimate in sapphires.
kawakawa - Maori name for the ordinary green variety of nephrite jade. See PUN
AMU; INANGA; KAHURANGI.
kawk - Cornish synonym for fluorite.
keeper - Band around wrist watch strap near buckle, to hold end of strap in
keeper ring - Originally, "Bride's ring." A diamond hoop worn above the wedding
ring. In modern times, a guard ring.
kerf - The groove in a diamond, cut in preparation for the cleaving.
Kew certificate - A certificate stating results of tests of timekeeping of a
watch or chronometer, issued by National Physical Laboratory at Teddington,
England. Prior to 1900 the tests were made at Kew Observatory, Richmond,
England, and the prestige there established for Kew certificates was so high
that the name was retained when the testing was moved to Teddington. The
certificates for passing tests, with highest requirements are designated Class
A; and for a less exacting series of tests, Class B.
keyhole plate - In weight clocks, the brass disc with an eccentric hole
intersecting the concentric hole of less diameter that slips into a groove on
the mainwheel arbor, to hold the mainwheel against the barrel, and permit
movement of barrel during winding.
keyless - Horology. Term used elsewhere than in America to describe watches
wound and set by a button (crown) on end of the stem, outside the case.
key-pattern - See GREEK KEY PATTERN.
key-regulator - A type of regulator, used mostly in Swiss watches with flat
hairsprings, in which the spring-terminal is in a space between ordinary
curb-pin, and a metal block called the key, boot, or gate-block, at the lower
end of which is a finger that may be turned to extend across the opening to
touch the curb-pin, to prevent the spring coil from jumping out if the watch
receives a shock as when dropped, etc. See CURB-PINS; REGULATOR.
key ring - An adjustable device to hold keys. In simple form these are made as
split rings onto which keys are introduced by forcing the split sections apart.
More elaborately, they are made of spring-loaded holders and threaded devices,
in gold and silver.
keystone - A system of quoting wholesale prices of jewelers' goods. It means
that 50 per cent of the price stated in a catalog or price list shall be
understood as the wholesale price. Originated in 1896 by Keystone magazine, a
predecessor of Jewelers Circular-Keystone, after subscribers had complained
against the showing of dealer costs in a publication that customers might see on
keystone cut - A fancy diamond cut, whose outline is that of a keystone.
key-stud - In an American-type watchmaker's lathe, the short pin in the spindle
throat that engages the slot on shank of chuck to prevent its rotation in
relation to the spindle.
keywinder - Watch wound and set with a separate key, differentiated from a
stemwinder (American) or keyless (English) watch.
Killicranke diamond - White topaz from Tasmania.
kilo - In the metric system, one thousand, as in kilocycle, kilogram, kilometer,
kilogram - One thousand grams, five thousand carats, or 2.2046 pounds.
kimberlite - Mottled greenish to bluish-grey or black rock filling the throats
of ancient volcanoes, a small proportion of which contain diamonds. It was
named for Kimberley, South Africa, where the first identification of such rock
had just been made. Similar diamond-bearing volcanic pipes or fissures have been
found elsewhere in Africa as well as India, Siberia and North America.
kinetics - The laws governing the energy possessed by a moving body due to its
king cut - An additionally faceted brilliant cut, with 49 crown facets and 37 pavilion facets instead of the customary 33 and 25.
king topaz - An erroneous name for yellow to orange sapphire.
kinradite - A local trade name for iron-oxide-stained yellow, red and brown
spherulitic jasper from California.
kite cut - A fancy diamond shape, resembling a boy's kite in outline.
klaprothine - Lazulite.
knee punch - Staking punch of a form to permit entering the shell of a cylinder,
for driving out pivot plugs. See CYLINDER ESCAPEMENT.
knife edge. - 1. An item of jewelry findings, wire of gold, etc., drawn so that
a cross-section resembles that of a knife blade or wedge. 2. A fulcrum for
pendulum suspensions, or for beam of precision weighing scales, affording
knife edge file - A form of file for cutting work in an acute angle, with
double-cut teeth on sides and single-cut teeth on edges.
knife-edge girdle - A thin, easily-chipped girdle of a gemstone; American Gem
Society regards 0.175 mm. as the minimum desirable thickness for the girdle of
a brilliant cut diamond.
knuckle - One of the tubular sections that form the hinge on the lid of a watch
case, locket, etc., in connection with the hinge-pin,
knurling - A milled or corrugated surface produced on the circumference of a
key or adjusting nut, to enable a firm hold with fingers in winding or
tightening; produced by pressing a notched steel roller, a "knurl", into the
blank while rotating in lathe.
Koloriscop - A light box for the color-grading of diamonds, patented by Dr. E.
Giibelin of Switzerland.
Korea jade - Misleading name for serpentine.
kornerupine - (kor'new-roop-peen") A rare and unusual gem, a magnesium aluminum
silicate, usually yellow or brown, but found in Madagascar in gemmy sea-green
crystals in a pegmatite. It is about 6l/2 in hardness; the gravity is 3.28 to
3.34, the refractive index L669 to 1.682. It crystallizes in the ortho-rhombic
system and has a strong pleochroism, green to yellow to reddish brown. It is of
interest only to collectors of unusual gems.
kouphotite - Prehnite.
krantzite - One of the amber minerals, of no gem importance.
kunzite - One of the gem varieties of the mineral spodumene. Kunzite was first
found in the tourmaline mines of Pala, Calif., and was named for George F.Kunz.
It is lilac in color, strongly pleochroic, the refractive index range is 1.660
to 1.675 and the specific gravity about 3.19. See SPODUMENE.
kyanite - (ky'an-ite) A common mineral, an aluminum silicate used in the
manufacture of heat-resistant ceramics, which is sometimes found in flat
elongated gemmy bluish crystals. The refractive indices are 1.712 to 1.728, the
specific gravity about 3.67, and the hardness most interesting. It is an
outstanding example of the difference in hardness in crystal directions, a
phenomenon usually too small to be observable by simple methods. Parallel to the
elongation of the crystal, the mineral can be scratched by a knife; its hardness
is about 4 to 5, while across the crystal its hardness is about 7, and a knife
leaves no mark.
L - Abbreviation for "let-off;" denoting the pallet (L-stone) in lever
escapement, whereon escape-wheel teeth act last, in their passage through the
escapement. See LET-OFF; R.
Labrador feldspar, Labrador moonstone - Labradorite.
labradorescence - (lab'ra-dor-ess"sense) The vivid coloration displayed by a
properly oriented section of labradorite. See ADULARESCENCE.
labradorite - (lab'ra-dor'ite) A gray plagioclase feldspar in which the
proportion of soda to lime is about 2 to 3. It is notable for the spectacularly
colored reflections visible on a properly oriented face viewed and illuminated
at the correct angle. According to Robert Webster, the optical effect that makes
these colors is "mostly due to interference of light from the fine lamellae of
the repeated twinning" and to platelets and needle-like inclusions of magnetite.
A deep blue or green, like a Brazilian butterfly's wing, is the most common
effect, but this may shade to green, yellow, bronze or red. Transparent
labradorite had been found in volcanic rocks in Utah, Oregon and New Mexico.
Faceted stones of this material are interesting to collectors. At Plush, Ore.,
there are crystal portions that show red and green, and cut stones remind
experts of andalusite. See BULL'S EYE; CHANGEANT.
Lake George diamonds - A fanciful misnomer for the brilliant, doubly terminated
colorless quartz crystals for which New York's Herkimer County is famous.
Lake Superior greenstone - Chlorastrolite.
lambrequin - A cartouche on some clock dials in the form of a curtain-drape
bearing the maker's name.
lambreu - Brazilian term for brilliant irregular fragmented diamonds.
laminated balance - Term sometimes used denoting a compensating balance. See
landerite - A name which has been given to the pink grossularite in white marble
which comes from Xalostoc, Morelos, Mexico. See ROSOLITE
landscape agate - A variety of moss agate which gives the effect of a scene, as
opposed to other types resembling figures, trees, etc.
lanisher - A belt sander used to smooth flat areas prior to polishing.
lap - 1. A horizontal spinning wheel about one foot or 18 inches in diameter
against which gems are polished. Diamond laps are composed of soft iron, which
best retains the diamond dust doing the actual cutting, and they rotate at high
speeds, 2000 to 2400 revolutions per minute. Softer gems are cut on similar laps
of varying metals, and at lower speeds. 2. Horology. See LAPPING. 3. Jewelry
making. A horizontal or vertical wheel 6" to 8" in diameter, charged with fine
abrasive, against which jewelry is polished to obtain flat, smooth surfaces.
Jewelry laps are made of felt, wood and metal. See LAPPING; SPLIT LAP.
La Paz pearls - The common trade name under which the often bronze-colored
pearls of the hammer-head clam, Malleus, are sold. They are found in the Gulf of
California, and the waters adjoining Guatemala, Panama and Venezuela, and are
also sold as Panama or Venezuela pearls.
lapidary - (lap'i-dare-ee) A person who cuts and polishes gems except, in trade
usage, diamonds. In older usage, a treatise on gems was called a lapidary.
lapis-lazuli - (lay'pis-laz"you-lie) Usually a mixture of lazurite with one or
more associated minerals, calcite and pyrite. It is an attractive blue stone
commonly used in decorative carvings and for beads and cabochon gems. The best
quality material is found in Afghanistan; other localities are Siberia, Chile
and California. See LAZULITE.
lapped border - An article is said to have a lapped or rolled edge when the
metal has been rolled over the edge and spun under to give the effect of a
lapper - A specialist in one phase of diamond finishing, the man who puts the 18
fundamental facets on the stone. They are the four top corner, the four bezel
and the table facets on the crown, and the four bottom corner, the four pavilion
and culet facets in the pavilion. The stones are then finished by the brillianteer, who puts the additional 40 facets on the stone. 2. Jewelry making.
A jewelry polisher specializing in lapping, the polishing of flat surfaces such
as are produced on watchcases and other articles calling for precise, flat
surfaces. See LAP; SPLIT LAP.
lapping - 1. Diamond polishing. The process of cutting the first eight top, the
first eight bottom, the table and the culet facets on a brilliant cut diamond.
See BLOCKING. 2. Horology. Abrasive process for shaping and finishing hardened
steel parts of timepieces. Laps are of two main forms: a flat slab of soft
metal, on which an abrasive is spread and the work rubbed on it, to reproduce
the flat surface of lap on the work; or a disc or wheel rotating on a spindle
and held in contact with the work. Coarse abrasive is used on laps for shaping
work, and finer abrasives for polishing. In the soft metal of the laps the
grains of abrasive imbed themselves under pressure of the work, so that their
sharp corners are held to cut the hard metal of the parts being lapped, thus
reproducing on the work the form of a lap. See ABRASIVE. 3. Jewelry. The art of
producing flat, smooth surfaces on jewelry by means of laps. See ABRASIVES.
laser - Term under which an optical maser has become known; an acronym for Light
Amplification by Stimulated Emission of Radiation. Using a fluorescent gas or
doped solid, such as a synthetic ruby crystal, it produces a powerful, intensely
hot, straight-line beam of light of very restricted diameter, capable of burning
its way through solid substances.
laser drilling - A method, developed in late 1960's, for improving the
appearance of a flawed diamond by boring a laser-beam hole into the inclusion.
Merely piercing the inclusion may cause it to turn white; other inclusions
must be leached out by acid or other volatile liquid. Drill holes, sometimes
only 0.5/1000 of an inch in diameter, may be scarcely visible under 10X; they
often appear as a "V", due to reflections from the entering-facet surface.
Laser gem - Promotional name for a doublet imitating a diamond.
lasque - A thin tabular diamond crystal; such material has been used in the past
to glaze miniature paintings; also called portrait stone.
latch - The device used on index-plate of a watchmaker's wheel-cutter to hold
the work stationary during the milling of each tooth-space.
lathe - A machine for rotating work to be shaped by turning, milling, polishing,
grinding, drilling, etc. In the watch and jewelry trades, the principal forms of
lathes used are the watchmaker's lathe for shaping and finishing parts for
timepieces, and the jeweler's polishing lathe for finishing work with buffs and
abrasives. Modem jewelry lathes are precision, high-speed instruments used to
turn wedding bands to size and shape and to effect diamond finishes inside and
outside of the ring. See ATTACHMENTS.
lathe-loupe - A watchmaker's magnifying glass made to attach to lathe instead of
worn over the workman's eye.
lathe mandrels - Metal tapers of graded diameters or of split expansion type,
for holding rings or the like during turning operations in a lathe.
lattice - Term used for the atomic arrangement within a crystal which is
responsible for the external shape and the directional optical and physical
properties of a crystallized substance; thirty-two variations are possible.
lava - (lah'va) Molten rock flowing from a volcanic vent, and the rapidly
solidified product of that activity. It sometimes contains crystals of gem
materials, such as chrysolite; a compact bluish glassy variety from Vesuvius has
been cut into cameos and intaglios. See OBSIDIAN.
lavaliere - (la-vahl-yare) An article of jewelry consisting of a pendant
suspended on a chain or light necklace; after the Duchesse de La Valliere
(1644-1710), a mistress of Louis XIV.
lax diamond - Term for a dull, fireless diamond.
lazulite - (laz'you-lite) Not to be confused with lazurite. Lazulite is a blue
monoclinic phosphate of iron, magnesium and aluminum, a little heavier but of
about the same hardness as the other mineral. Its blueness is not as intense as
that of the best lapis lazuli, and it is not associated with pyrite. Usually it
is of no gem significance in the trade, but discoveries in Death Valley indicate
a potential supply of attractive decorative material. Other localities are
Brazil, where it has been found in deep blue transparent pebbles and masses,
Georgia and Austria. Brazilian diamond specimens showing a matrix of lazulite
are probably faked. Available, very rarely, in faceted deep blue, strongly
pleochroic gemstones, with a r.i. of about 1.63, hardness of 5%, and a density
lazurite - (laz'your-ite) The principal, to exclusive, mineral ingredient of
lapis lazuli. Lazurite is a deep blue sulphur-bearing sodium aluminum silicate,
the color of which is caused by the sulphur present. Two related minerals may
partially replace lazurite without destroying the molecular structure, and
consequently, the dodecahedral crystal habit. Its hardness is about 5%, the
specific gravity about 2.4 (lapis lazuli containing pyrite, over 2.7) and the
refractive index 1.50. See LAPIS LAZULI.
lazurquartz - Sapphire quartz.
lazurspar - Lapis lazuli.
leaching - 1. A technique, introduced about 1940, for improving the appearance
of some flawed diamonds; hydrofluoric acid is used to reach inclusions open to
the surface or from which fractures or cleavages radiate to the surface; thus
unsightly flaws may be "leached" white. No means of detection is known. 2. Acid
or other secret liquid used, since the end of the 1960's, to leach out certain
inclusions that have been reached by laser beam. See LASER DRILLING.
lead - A heavy, pliable, inelastic metal, having a bright, bluish color, but
lead glass - Imitation gemstones. A high-index glass containing a
considerable proportion of lead oxide. Its refractive index and hardness vary
with the lead content. Flint glass is a frequently used formula of a lead glass;
the refractive index is about 1.62 and the specific gravity about 3.4.
lead screw - A turning machine screw in a mechanism which advances or retracts
a device attached to it.
leaves - Horology. The cogs on a pinion in gearing, differentiated from cogs on
a gear wheel, which are called teeth. See GEARING.
lechoso opal - (lay-cho'so) A name of no particular significance, but about
which there seems to be some difference of opinion. Lechoso probably is derived
from a Spanish word for milk, and so should mean a milky, almost clear opal of
the Mexican type. Schloss-macher, however, attributes this name to the Mexican
fire opal which shows some of the color flashes of precious opal in the red
ground color. Others restrict the term to opal showing green to violet color
flashes in a colorless mass.
L.E.D. - See LIGHT EMITTING DIODE.
left-hand screw - A screw with thread made to turn counter-clockwise, contrary
to most screws in this respect; used in some watches to hold parts in the
stem-winding and setting mechanism the motion of which would tend to unscrew a
right-hand threaded screw.
left-handed fuzee - A fuzee movement in which, dial down, the third wheel is at
the left and the balance is on the right.
lemel - Miscellaneous sweepings from jewelry shops, including filings, chips
from engraving, bits of solder, etc., too small to be treated by known kind and
quality of metal. Lemel is "sweep-smelted" and refined to reduce and separate
what is in the mixture, for recovering the value of the metals. See SCRAP.
lentil cut - A cabochon cutting in which both sides have the same convexity,
usually a rather flat thin cabochon stone, of the type of many opals.
lentille - Form of watch crystal for open-face cases, in which the edges inside
the bezel are rounded off; made originally like mi-concave glasses with a
sharp-cornered beveled edge, the polishing off and rounding of this corner is
what produces a lentille crystal. See WATCH CRYSTAL.
lepidolite - (leh-pid'oh-lite) A lithia mica commonly found in pegmatite dikes
and an associate of colored tourmalines, etc. Often attractively colored in
shades of lavender, compact masses have sometimes been used in decorative
carvings, though its mica softness is conducive to neither a high polish nor
Lepine calibre - A movement first designed by Jean Lepine (1720-1814), in which
each wheel has its own "bar" or bridge,
let-down plier - A plier devised for releasing the tension of a clock mainspring
preparatory to disassembling the clock.
let-off - In the action of a lever escapement, the cessation of contact between
an escape-wheel tooth and a pallet; the corner of pallet where this occurs is
called the let-off or "L" corner. This term also distinguishes the one of the
pair of pallet stones where all teeth of the escape-wheel in turn are let off or
discharged from action in the pallets; hence called the "L" or let-off pallet
stone, differentiating it from the receiving or "R" pallet stone, at which all
escape-wheel teeth are received into action with the pair of pallets.
leuco sapphire - (lue'ko) Colorless sapphire.
leveler - A tool with a small slot on the end of a steel wire, at a right-angle
to the length of the wire, used for making slight bends on hairspring coils, to
bring them all into the same plane when truing a hairspring.
lever - Horology. In the pallet-fork-and-arbor assembly of lever escapement,
the lever is the steel bar between the fork and the pallet.
lever escapement - The escapement long established as best for use in watches;
invented by Thomas Mudge, London, England, about 1765, a detached type
escapement, with pallet-fork-and-arbor assembly between the escape-wheel and
the balance. See DETACHED ESCAPEMENT; ESCAPEMENT.
lever-fork polisher - A tool comprising two flexible laps, for polishing the
inside acting surfaces of a fork-slot of a lever escapement.
Leveridge gauge - An instrument which permits a weight estimate from the
dimensions of a cut stone; invented by Athos D. Leveridge in 1937.
lever-set - Type of hand-setting mechanism for watches, in which a lever is
pulled out from side of dial, to shift the mechanism from winding to setting
condition. This type of setting is favored by railroad watch inspection rules,
because with it, it is impossible to leave watch in setting position
accidentally, which could cause an error in timekeeping. See PENDANT-SET.
LI - Abbreviation for "lightly included." See CLARITY GRADE.
lift - The phase of wheel-and-pallet action in a lever escapement that takes
place while an escape-wheel tooth is passing over the lifting face of a pallet
stone. See IMPULSE.
lifting-piece - In a striking clock mechanism, the lever that lifts the
rack-hook, preparatory to striking.
lifting spring - In a hunting watch case, a spring that lifts the lid over the
dial, when the locking spring is released.
ligament pearl - A pearl which formed near the hinge in the ligaments. Such
pearls are usually elongated distorted masses of no particular value.
light brown - A commercial color classification of diamonds; according to Eric Bruton, between fine light brown and dark brown and equivalent to cape in the
light cape - A commercial color classification of diamonds; according to Eric Bruton, between silver cape and cape.
light-emitting diode - A tiny dot or bar of a chemical-metallic element that
glows when stimulated electrically, used in digital displays of some solid
state timepieces. There are a number of diodes for each digit and from them any
numeral from 0 to 9 can be arranged. Because light-emitting diodes require
current in the milliamp range, and because a tiny battery can supply only about
100 milliamp hours per year, there cannot be a continuous time display.
Therefore, watches with light-emitting diodes show time only upon command, as
upon the pressure of a button.
light opal - White Cliffs opal.
light platinum metals - Ruthenium, rhodium, and palladium, metals of the
platinum group, but of considerably lower specific gravity than platinum.
lights - Term used by chronometer makers to denote the spaces between the edge
of an impulse roller and the points of the nearest two escape-wheel teeth when
the escape wheel is at rest between unlockings. In adjusting the chronometer
escapement, these lights or spaces should be made equal.
light yellow - A color classification in the Scan, D.N. system equivalent to 0,
P, Q and a portion of R in the GIA system or to 8 and a portion of 9 in the
American Gem Society system.
ligne - (leen'y; line) An ancient French unit of measurement, still used for
designating the diameters of watches, especially watches of European origin. A
ligne is the equivalent of 2.255883 millimeters, or .08883 inch. See WATCH
lilalith - Lepidolite.
lime - Calcium magnesium oxide, sometimes used in place of crocus as a polishing agent.
lime, Vienna - A compound of oxide of calcium and magnesium, obtained by
exposing slaked lime to air, formerly used extensively by American factories for
limonite - (lie'monite) A brown hydrous oxide of iron of indefinite composition.
It is a common ore of iron and is often found as a thin coating over gem
minerals, imparting a yellow tinge. Commonly associated with turquoise, it is
often the brown matrix material so frequently cut with that gem.
Linde Star - Synthetic star rubies and sapphires produced, 1947-1975, by the Linde division of Union Carbide Corp.; marked with an L on the back, to
distinguish them from those made by other manufacturers.
liner - A graver used for engraving a series of parallel lines close together,
with a single cut of the tool.
line finish - A finish used on parts of timepieces, consisting of a series of
fine parallel lines, scratched on the metal surfaces by rubbing the part, with
motions strictly in one direction and reverse, on a flat surface charged with
an abrasive; or by rubbing an abrasive lap similarly on the work. See POLISHING.
line-of-centers - An imaginary line passing through the centers of wheels and
lintonite - (lin'ton-ite) A name for the mineral related to thomsonite which is
found in green and pink banded pebbles on the shores of Lake Superior and often
cut and used locally for a gemstone.
lips - Horology. The edges of the half-shell portion of cylinder in a cylinder
escapement, which act as pallets while being given lift by the inclines on the
escape wheel teeth. See CYLINDER ESCAPEMENT.
liquid crystal - A type of display used in some solid state timepieces in which
time is shown by means of a sophisticated liquid sealed wafer-thin between two
slender glass plates. Sealed in with this liquid, but glued to the inner surface
of one of the plates, is a set of current-carrying but transparent segments of
numbers, connected by tiny wires to the circuit. When selected segments are
stimulated electrically, the liquid in front of these segments changes from
clear transparency to opacity, or becomes light-reflective, to form numerals
denoting the time. Because the liquid crystal display needs current only in the
millionths of an ampere, liquid crystal displays can remain on constantly. See
DYNAMIC SCATTERING; FIELD EFFECT.
liquid inclusion - An inclusion within a crystal that is filled with a liquid,
usually recognizable as such only if there is also a gas bubble present, which
can move about, or some solid material that can be seen to slowly tumble down as
the specimen is turned.
Lisbon cut - A modification of the brilliant cut, giving the stone 74 facets.
lithion beryl - Name given to a lithium-containing and caesium-free variety of
beryl, from Schlossmacher's analyses. It would seem to be generally an
lithia mica - Lepidolite.
lithia lazuli - Violet fluorite.
lithoxyle - (li-thoks'ill) Opalized wood in which is preserved the grain of the
litoslazuli - A misleading term which has been applied to the purple massive
fluorite from Sierra de Cordoba, Argentina, in reference to a fancied
resemblance to lapis lazuli.
liver opal - Menilite.
live-spindle lathe - A watchmaker's lathe of the American type, in which the work-holding spindle rotates with the work; differentiated from the dead-center
or European type lathe, in which the spindles are stationary with the work
rotating on their centers. See DEAD-CENTER LATHE.
loam - An ocreous earth prepared for painting on soldered joints in jewelry
work, to protect a joint from heat while additional soldering work is being
done. See OCHRE; YELLOW OCHRE.
lock - Horology. The condition in action of a lever escapement during which the
motion of escape wheel is stopped by contact of one of its teeth with the
locking-face of a pallet stone. See UNLOCKING.
locket - A piece of jewelry worn suspended on a neck chain, comprising two lids
hinged together, for containing a portrait, lock of hair or other personal
locking jewel - In a chronometer escapement, the upright flat-faced pin of ruby
or sapphire, set in the detent, against which an escape wheel tooth rests during
locking of the escapement.
locking, equidistant - Lever escapement design which has the locking corners of
each pallet jewel equidistant from the pallet (arbor) center.
locking spring - In a hunter-type watch case, the spring that presses the catch
into its seat upon release of the crown in closing the case; the catch engages
the lid of case to hold it closed.
lodestone - Magnetic magnetite. Magnetite is a black oxide of iron which is
attracted by a magnet and which is an important ore of iron. Some specimens of
magnetite are themselves magnets, they are then known as lodestones and are
often sold to the gullible as good luck charms.
long case clock - The proper term for a tall clock standing on the floor,
otherwise known as floor clock, hall clock, grandfather clock.
long-nose plier - A form of plier much used in clock repair work, with jaws of
extra length for reaching between plates.
loops - Items of jewelry findings, for suspending lockets, etc., to necklace
chains; usually soldered to the locket.
lorgnette - (lorr-nyett’) Eyeglasses made with the framed lenses hinged to fold
into a handle, used by holding the lenses to the eye instead of wearing them as
spectacles or pince-nez.
Lossier curve - The technical terminal curves of a Breguet hairspring.
lost wax casting - A process of casting whereby a wax model is encased in an
investment similar to plastic, the investment is agitated mechanically or put
into a vacuum to remove air bubbles and placed in an oven where the wax is
burned off, leaving a cavity which is filled through an opening with molten
metal. Then the investment is broken away from the hardened metal, which is
ready for polishing and stone setting. For large-scale production, numerous
identical wax models are made by pouring molten wax into a rubber mold; all are
placed in the investment as a tree-like group. This process is also known by its
French equivalent, cire perdu.
lot pearls - Small pearls, below 1 carat in weight.
Louis XIV hands - A style of clock and watch hands designed in the manner of the
period of Louis XIV of France. For illustration, see HANDS.
loupe - A jeweler's or watchmaker's magnifying-glass worn over one eye; with a
single lens or a system of lenses for greater magnifying power.
loupe clean - A term used to describe a diamond that shows no flaws under
magnification; its misuse to deceive is prohibited by the Federal Trade
Commission; the American Gem Society prohibits its use by members. See FLAWLESS.
love arrows - Sagenitic quartz.
love stone - Aventurine quartz.
lower girdle facets - The 16 triangular facets that border the lower side of the
girdle of a round brilliant cut diamond. Before about 1935, they often were cut
to form points half way down, between the eight pavilion facets. But current
practice is to lengthen them to approximately 80 per cent of the girdle-to-culet
distance, for an increase in brilliance with some loss of weight. Also called
bottom-half, bottom-break, lower break facets. See GIRDLE FACETS; BRILLIANT.
low relief - A form of ornament in which designs are raised above a background
surface, but raised less than one-half of what would be their full "thickness;"
for instance, of a human face on a cameo. This is often stated as bas-relief.
See HIGH RELIEF. 2. The appearance of an inclusion in a gem with a refractive
index near that of the host material.
low - square setting. A replica of the upper half of a square prong setting.
Frequently used for repair or replacement jobs.
lozenge - 1. A fancy diamond cut, like the diamond of a pack of playing cards,
in outline. 2. A diamond-shaped decorative motif. 3., Facet.
lozenge graver - A graver of diamond-shaped cross-section, affording a long slim
point, for cutting inside a narrow space.
L-rest - Hand rest, L-shaped to allow closer entry of cutting tool into a
L.S.I - Large scale integration. Type of sophisticated circuitry in quartz
lucky stone - Twinned staurolite.
lug - 1. The extensions of a watch case to which is secured the bracelet.
spring bars attached to the lugs.
lumachelle - Fire marble, fossiliferous limestone with the preserved, unaltered,
iridescent shells of molluscs, usually ammonites or baculites. See AMMOLITE.
luminescence - The emission of visible rays by certain stones or other materials
that have been excited by invisible rays. The phenomenon is called
thermoluminescence if the stimulus comes from heat rays beyond the red end of
the spectrum; triboluminescence, if the light results from impacts. The
phenomenon is called fluorescence if it coincides with the stimulus of rays
beyond the violet end of the spectrum, and phosphorescence if it persists after
the removal of that stimulus.
luminous dial - Any dial the indicators of which are coated with material that
glows in the dark, often radioactive until the Nineteen Thirties, thereafter of
some non-radioactive material such as tritium or other phosphorescent exciter.
luminous hands - Watch hands made of skeleton form, the openings holding a
filling of a phosphorescent exciter, for use with dials with luminous numerals.
For illustration, see HANDS.
lumpy. A stone which is cut so that it has too much depth for its spread.
lumpy girdle - Too thick a girdle.
lunar disk - The moon phase disk in a timepiece.
lunar stone - A phosphorescent variety of barium sulphate, barite. See
lunette - A watch glass with slight top curve but sharply curved at the edge.
luster - 1. The appearance of a surface in reflected light, divided into two
principal groups, the metallic and the non metallic. Non-metallic lusters may be
vitreous, resinous, pearly, greasy, silky, or adamantine. Minerals with
refractive indices from 1.3 to 1.8 will have vitreous luster, from 1.9 to 2.5
adamantine luster. Pearly luster is seen on the cleavage planes of minerals
having pronouncedly good cleavage, silky luster in minerals with a fibrous
structure. 2. Pearl By blocking the light source with one's head and holding a
strand 6-9" in front of the eyes, the head and shoulders may be seen reflected
in a lustrous pearl. The GIA appraisal system uses six grades of luster: Very
Bright, Bright, High, Medium, Slightly Dull and Dull. Most strands fall in the
Medium range. 3. Diamond. Diamond's adamantine luster gives it a brilliance unobtainable
in other stones. No substance can be polished more highly or keep its polish so
long against every adversary.
lute - A refractory cement or clay for packing a joint or sealing a cover to a
crucible. 2. Luting, to protect parts from heat when soldering by coating with
lychnis - Ancient name for a red gem stone, either spinel or rubellite.
Suspected to be the latter from Pliny's description of it as a stone which
attracts chaff and bits of paper when heated in the sun or by friction.
Lydian stone - Touchstone.
lyncurion, lyncurium - An ancient Greek name, mentioned by Theophrastus, for a
brown gem, possibly zircon, which was supposed to have been formed from the
congealed urine of the lynx.
lynx eye - Labradorite with a green schiller color.
lynx sapphire - Said to be applied to a light blue sapphire or, more fancifully,
to cordierite. Another authority applies it to dark blue sapphires. Neither
usage is desirable.
lynx stone - Cordierite.
maacle - Same as MACLE.
mabe - Japanese term for half-pearls, pearls that have been cultured against the
shell so that only a hemisphere of nacre grows. They are cut out and often
backed with a lower half of mother-of-pearl cut from a large Margaritifera
shell, to make an apparent round pearl and then mounted in a setting, like a
ring, which requires only an upper half to show.
Macassar shell - Mother-of-pearl shell coming from the northern and western
coasts of Australia, Margaritifera maxima, the largest pearl oyster, which also
lives along the Malay coast and which is named according to the trading center.
Also known as Sydney, Queensland, Port Darwin, New Guinea, West Australia,
Manila or Merghui shell. Slight differences characterize the localities; the
Australian is uniformly silvery white, the Macassar is more iridescent, and the
Manila has a wide yellow border.
Machastone - Moss agate.
macle - (mahkl) 1. French for twin. Many mineral crystals are intergrown in twin
relationships, but the trade, speaking of macles, means diamonds which are
twinned according to the spinel law. They take the form of flattened triangles
and a perfectly developed pair will show re-entrant angles at the corners. The
twinned growth breaks the cleavage direction and makes the stones harder to cut
into good gems. 2. A classification of rough diamonds, triangular flat stones
which are such twinned crystals.
Madagascar amethyst - A distinction which can only be made by experts. Dark
amethyst from Madagascar is supposed to have a somewhat smoky tinge; the lighter
shades resemble the Siberian, often having a pronounced reddish-violet hue and
Madagascar aquamarine - A trade term for a dark blackish-blue, rather than pure
Madagascar citrine - After Brazil, Madagascar is the most important locality.
Said to be somewhat more brilliant and more like topaz in color; the quality is
often improved by burning.
Madeira topaz - Misnomer for naturally brown quartz crystals from Spain, the
original "Spanish Topaz," with a Madeira-wine color— the name refers to the
color, not a locality. Since 1900 the name has also been applied to the darker
burned Brazilian amethyst.
Madras pearl - 1. Persian Gulf pearls, many of which come into the trade through
Madras or Bombay. 2. Trade name for selected natural oriental pearls of the
magma - (magg'ma) Liquid rock material within the earth from which igneous rock
or lava is formed. See IGNEOUS ROCK.
magnetic balance - A watch balance impelled by its magnet's attraction or
repulsion from an electromagnet.
magnetic banking - In an electric watch, the positioning by a magnet of the
magnetic chuck - A lathe-chuck holding its objects by magnetic attraction.
magnetic corrector - In astronomical clocks, a permanent magnet attached to the
bottom of the pendulum, below which is an electromagnet in which a weak current
may be introduced at will, to modify the effect of gravity on the pendulum, to
influence the rate of the clock,
magnetic escapement - Any electrically motivated escapement in which wheels are
advanced through magnetic influence.
magnetisation - Horology. The condition a watch may be in from too close
proximity to heavy electric currents and magnetic fields, in which the steel
parts become magnetic, and exert forces on each other that ruin accuracy of
timekeeping. Magnetism may be removed rather easily by demagnetizing. See
magnetostrictive - A change in dimensions in a ferrous metallic transducer under
magnetic influence. The metallic transducer in some ultrasonic cleaning
magnifier - See LOUPE.
maiden pearl - A newly fished pearl.
main facets - The bezel and pavilion facets of a brilliant-cut diamond.
mainspring - The spiral coil of steel "ribbon," the unwinding of which furnishes
motive power for portable timepieces. The first use of a spring for this purpose
was made by Peter Henlein, of Nurnberg, Germany, shortly after the year 1500,
who thus made the first watch. About the middle of the 19th Century, the trend
began of making mainsprings longer and weaker, replacing the shorter, thicker
springs with which, for the previous three centuries, had to be used the FUZEE
or other power-equalizing device, to compensate for the great difference in
power with the spring fully wound or nearly run down. The more modem idea is to
use a spring running much longer than just about a day, so that its weaker phase
is not reached by the time it should be rewound, in this way obtaining more
uniformity of power, A matter that helped in doing away with the fuzee and using
longer mainsprings was the discovery of adjusting to isochronism, which made it
less essential to seek uniformity of power and the unattainable uniformity of
arcs of balance motion. See FUZEE; HENLEIN; ISOCHRONISM.
mainspring barrel - A casing of metal, recessed out to contain the mainspring of
a timepiece, with or without its outer rim cut with gear teeth to form the
"first" wheel in the train. See GOING BARREL; MOTOR BARREL. mainspring brace. A
metal part attached to the outer end of a mainspring, to strengthen the hold of
the outer end of the spring in the barrel rim, by engaging in slots in the
barrel bottom, or cover, or in both.
mainspring gauge - An instrument for measuring the thickness and width of watch
mainsprings. The principal types are notch gauges, and simple forms of
jaw-gauges. Watchmakers are more and more adopting machinists' micrometer
calipers for gauging mainsprings in fractions.
mainspring hook - A metal hook either on the periphery of a barrel arbor hub, or
inside the rim of the barrel, engaging in a hole at either end of the
mainspring, to hold the spring in action during the winding and running of a
mainspring punch - A special pliers with a variety of dies and punches for
quickly piercing holes in ends of mainsprings for engaging the hooks of barrels
mainspring winder - A tool for winding a mainspring for replacement in its
barrel, instead of twisting the spring into the barrel with the fingers, which
may result in malformation of the spring coil.
maintaining power - Horology. Mechanism of various designs for providing motive
power to keep a clock running during winding, when winding would place a reverse
direction of power on the train and stop the clock, in the absence of
maintaining power mechanism.
main wheel - In the gear-train of a watch or clock, the toothed wheel which
forms a part of the first mobile in the train. In clocks the main-wheel is on
the weight-cord drum or mainspring arbor; in modern watches on the mainspring
barrel. The main wheel is the "first" wheel of the train; usually the center
wheel is second, and so on.
Majorica - The trade name of a particular brand of imitation pearls manufactured
in Majorca, Considered by their makers to be superior to ordinary imitations,
they are intensively advertised and the name is protected, but unsophisticated
buyers are often led to buy imitation pearls made in Majorca under the illusion
that they are this particular manufacturer's product.
make-and-break - Attachment to a clock or chronometer, a special switch to
obtain electric impulses for actuating a recording chronograph, or to make
malachite - (mal'a-kite) A soft green basic carbonate layers and so exhibits a
banded appearance when cut and polished. It is an important ore of copper at
some localities. See AZURITE.
malacolite - (mal-lak'o-lite) Diopside.
malakon, malacon - A brown glassy variety of zircon.
male sapphire - A darker colored stone, as opposed to the lighter, known as
female. The sexual attribution of gems is supposed to have been started by
Theophrastus, who developed a theory of stones' breeding
male stem - A winding stem for a watch in which the square on the stem fits into
a hollow square in a bevel or clutch pinion in the watch movement.
malleability - Property of some metals of being extended or shaped by beating
with a hammer, or by the pressure of rollers. By hammering, gold is the most
malleable of all metals, having been beaten into leaves 1/300,000 inch thick.
However, by rolling, lead takes first place; gold, third, See DUCTILITY.
mallet - A hammer with a heavy head made of non-metallic material, used for
cold-forging operations on soft metals, etc., to avoid denting the work as
would be done by a steel hammer. Jewelers use mallets with heads of tightly
bound rawhide, in connection with a steel mandrel, for forming and sizing rings.
maltesite - Chiastolite.
Maltese cross stop-work - A device used mostly in high-grade Swiss watches for
limiting the run of the mainspring to the force delivered by the coils when
neither fully wound up nor run down. Name derived from the resemblance of the
"star-wheel" to a Maltese cross. See FUZEE; MAINSPRING; STOP-WORK.
Manchurian jade - A hard brown soapstone.
mandrel - 1. An arbor on which work to be formed in a lathe or other machine is
mounted to support and rotate the work during cutting, grinding, etc. The work
is usually such as has a hole in it through which the arbor passes
friction-tight. 2. A steel rod slightly tapered, used by jewelers as an anvil
for forming rings by blows with a rawhide mallet. 3. A watchmakers' lathe of
Swiss origin, used exclusively for flat facing turning such as recesses in watch
plates; has hand-driven universal face-place, and slide rest; has no facilities
for other work than above stated. See LATHE.
manganese garnet - Spessartine.
manganese spar - Rhodochrosite.
manganese silicate - Rhodonite.
mantle - The outermost tissue layer of a pele-cypod which contains
manufactured stone - Gemology, Any kind of an artificial stone; synthetic,
Manufacturing Jewelers and Silversmiths of America, Inc - A national association
of more than 1000 manufacturing jewelers and silversmiths, headquartered in
Providence, R.I.; founded in 1903; publishes monthly American Jewelry
Manufacturer; sponsors trade shows in Providence, New York and elsewhere.
Maori stone - Nephrite.
marcasite - (mar'cass-ite) Trade term for cubic pyrite crystals, mounted in
groups, cut or uncut, in pins and other pieces of jewelry. An iron mineral with
bright metallic luster, its hardness is 6 to 6'/2, its specific gravity 4.9 to
5.2. Source, South Tuscany, Italy; cut by semi-automatic machinery in Turnov,
Czechoslovakia, and the Jura Alps, France. Mineral-ogically speaking, the term
marcasite is applied to another iron sulphide which has the same chemical
composition as pyrite; resembles it in color, luster and hardness; but
crystallizes in the orthorhombic system and has fewer specimens suitable for
marekanite - A decomposing perlitic obsidian, clear pebbles of which, gray,
brown, yellow and red in color, are found along the banks of the Marekanka River
in eastern Siberia.
Margaritifera - A pelecypod genus to which the precious pearl-bearing oysters
belong. Different strains produce recognizably different color varieties.
Mgarcharium pearls are yellow (Shark's Bay, West Australia), M margaritifera are
silver white (north coast of Australia; shell is largest and more important than
its pearls), M. martensii pearls are greenish white (natural pearls from Japan;
cultured pearls in this oyster are white), M. maxima are silver white (North
Australia), M. vulgaris pearls are pale creamy white (Gulf of Monaar),
maria glass - An early name for mica and selenite.
marialite - The sodium end-member of the scapo-lite mineral family.
Mari diamonds - Misnomer for rock crystal from near Kalabagh and Mari, India.
marine chronometer - A very accurate portable timepiece used for navigation of
ships, for carrying the time of a known meridian to use in connection with local
time of the ship's position obtained by observation with a sextant. The main
characteristic of marine chronometers is their escapements, which are of the
detent type. See CHRONOMETER; DETENT; ESCAPEMENT; NAVIGATION.
Marmarosch diamond - Misnomer for quartz.
marquise - A design of setting for cluster stonework in rings, etc., in which
the stones are set in a pattern like the outline of a marquise-cut diamond.
marquise cut - (mar-keez’) An elongated, doubly-pointed variation of the
brilliant cut, a popular diamond shape.
Mascot emerald - Trade name for an emerald triplet, supposedly made from genuine
beryl. If any of these are in the trade, they are very rare; quartz is the
common material used in emerald triplets.
mass aqua (marine) - Popular name for a hard glass imitation of aquamarine with
a hardness of 6, and a refractive index of 1.50.
massive - In reference to a mineral, one speaks of non-crystallized, though
often crystalline, material as massive.
massive amber - A compact variety of Baltic amber.
mass opal - Opal matrix.
master clock - In a system of a number of clocks corrected or operated by an
electric circuit, the master clock is the one, at a central point of the system,
whose timekeeping rate is conveyed to all of the secondary clocks on the
circuit. In synchronous electric clocks, driven by domestic service current, the
master clock at the power plant regulates the speed of the generators so they
will deliver the alternating current at the correct rate of cycles per second
for which the secondary clocks are designed.
Matara diamond - Also spelled Matura; misnomer for zircon.
matching - Horology. A term used in watch factories denoting the adjustment of
the escapement, as one of the processes of assembling or "finishing" watches.
In the watch repair trade, this work is called escapement adjusting.
materials - Horology. Replacement parts for repairing watches and clocks, as
kept in stock for sale by "material houses" or dealers.
matinee length - Pearl necklace, 22" to 23" in length. See PRINCESS; CHOKER;
matrix - (may'trix) The rock in which the gem is imbedded, often some of this is
polished along with the gem to make such stones as opal matrix, turquoise
matrix, emerald matrix, etc.
matting, matt-finish - A finish given to a metal surface by producing on it a
multitude of small pits, making a frosted or grained appearance, instead of
polished or line-finished. See LINE FINISH; SANDBLASTING.
Matura diamond - Misnomer for colorless zircon, mostly heated stones though some
naturally colorless stones may occur in the southern part of Sri Lanka known as Matara. Colorless zircons in small, almost microscopic, crystals are common in
many rocks and their derived sands.
mauve jade - A pale lavender color phase of jadeite,,
maxixe aquamarine or beryl - A name which has been applied to a deep blue, boron
bearing beryl from the Maxixe Mine, Minas Gerais, Brazil. It is strongly
dichroic in pink and blue. All are said to have faded after a short exposure to
light, and the color can be restored by irradiation in this particular type of
aquamarine. Deep blue aquamarines, even those naturally deep blue, are
consequently suspect, for paler blue aquamarines of this type could, for a time,
be made to look darker by an irradiation treatment.
mayaite - (my'a-ite, not may'a-ite) Name proposed for the Central American jade
rock, which is chemically unlike that of the Orient. It differs in the presence
of considerable amounts of diopside, the magnesium silicate, with the jadeite
molecules, and usually there is more or less albite in solid solution with the
pyroxene. It varies in color from white to yellow green and gray green. The
locality from which it comes is unknown, probably one or two places on the
Pacific coast of Central America. See MEXICAN JADE; TUXTLITE.
Mazarin cut - A 34-faced rather blocky brilliant type of diamond cut commenced
in the middle of the 17th Century under the aegis of Cardinal Mazarin.
mean-time screws - Screws with threads fitted friction-tight in a balance rim,
to be turned in for regulating watch to go faster, or turned out to go slower.
Usually there are two meantime screws, located at the ends of balance arms;
occasionally, two additional screws each half-way between ends of balance arms.
mechanical advantage - The ratio of the expending working force to the force
applied to a mechanism.
mechanical dop - See DOP. A mechanical dop is a small vise in which the stone
may be held at any angle, held in place by jaws and fastened by a bolt, in place
of the older method of embedding the stone to be cut in a low melting point
medfordite - Local Oregon name for a massive white quartz with streaks and
patches of green and brown moss.
Medina emerald - Misnomer for a green glass imitation stone.
mega - A million times a given unit (cycle, ohm, watt, etc.).
meionite - (my'on-ite) The calcium endmember of the scapolite family of
minerals. See MARI-ALITE.
melange - Assortment of mixed sizes of diamonds, larger than melee.
melanite - (mell'ann-ite) A black andradite, but probably the stone has never
found any gem use.
Meleagrina pearl - (mel'e-a-green"a) Synonymous with Margaritifera.
melee - (mell'ee—anglicized pronunciation) Term derived from French word for
"mixed," now generally applied in the diamond industry to round diamonds,
whether graded and sized or not (single, Swiss or full-cut), up to 1/6, 1/5 or
even 1/4 carat in size. Diamonds larger than melee are called SIZES. The term
SMALL MELEE or SMALL is often applied to diamonds weighing I/16th ct. or less;
these commonly have only 18 facets, including table and culet, although
fully-cut 58-facet stones are commercially available as small as I/100th ct. See
FULL-CUT; SINGLE-CUT; SIZES; SMALLS; SWISS CUT. The embellishing diamonds
mounted in any article or jewelry are collectively classed as melee.
melichrysos - (mel-i-kris'os) Ancient name for yellow zircon.
melle - Brazilian term for poor quality diamonds.
melting snow jade - Fanciful name for a jadeite quality which is characterized
by a white to gray color, with irregularly distributed opaque white patches
veined and cut by more translucent streaks. The name is apt and well de¬scribes
menilite - (men-ill ite) An opaque gray or brownish common opal which takes a
fine polish, occurring in colloform masses at Mont Menil in Paris.
mercurial gilding - See MERCURY GILDING,
mercurial pendulum - A compensating pendulum, invented by George Graham, about
1715, the bob of which is a vessel containing a column of mercury. As increase
of atmospheric heat lengthens the pendulum rod, it also raises the centre of
mass of the mercury column, which compensates for the lengthening of the rod,
and vice-versa. Adjustment comprises adding or removing mercury, until
compensating effect is correct. See GRAHAM, GEORGE; PENDULUM.
mercury - A white elemental metal, which is liquid at ordinary atmospheric
temperatures. In horology, it is essential for mercurial compensating pendulums
and mercurial switches.
mercury contact - An electric switch for obtaining a record of pendulum
vibrations, or other purposes in clockwork, having a metal point on the
pendulum to sweep through a cup of mercury; or a sealed tube of mercury which
tilts with the movements of the pendulum and opens and closes a circuit between
points inside the tube.
mercury gilding - This, the oldest gilding process, used since Roman times, was
the chief method by which metals were coated with gold before the invention of
electroplate. An amalgam of gold dissolved by mercury (about one-third mercury
and two-thirds gold after final treatment) and a solution of nitrate of mercury
were brushed repeatedly upon the work, which was then heated over charcoal until
the mercury was driven off, leaving a deposit of gold. The gold formed an alloy
at the point of contact, making a tough, cohesive coating. The layer could be
varied in thickness, so that it was possible to coat the other metal with a
heavy deposit of gold. Because poisonous fumes took the lives of many craftsmen,
the process was outlawed in several countries. See VERMEIL.
Mergui shell - Shell of the M. maxima species marketed in Burma.
metallurgy - The art and science of extracting metals from their ores and
preparing them for use by the manufacturer, who fashions them into finished
articles. It includes smelting, amalgamation, electrolytic refining, etc.
metamorphic - Literally, changed form. In geology metamorphic rocks are those
which have been altered from their original character (usually sediments) to an
igneous rock mineral makeup by heat and pressure within the crust, consequences
of mountain-making forces. Migrant volatiles play their part in this
high-temperature reshuffling of elements.
methyl alcohol - Chemical term for wood alcohol. Important in horology and
jewelry work mostly as the substance added to pure grain alcohol (ethyl alcohol)
to make denatured alcohol, which is used for rinsing cleaned watches, jewelry,
methylene chloride - A colorless volatile liquid used as a degreaser or
refrigerant. Will also melt many plastics.
methylene iodide - (meth'ill-een) An expensive organic iodine compound with a
high refractive index (1.742) which is used when testing gems on the
refractometer, and a specific gravity of 3.324 making it valuable as heavy
liquid for gravity determinations.
metric carat - The present internationally ac¬cepted unit of weight for gem
stones, 200 milligrams or five carats to the gram.
metric grain - A pearl weight, equal to one-quarter of a metric carat.
metric measurement - Measures of length based upon the meter, with units or
subdivisions expressed in multiples of ten. In horology, it is especially
convenient to use the millimeter (one thousandth of a meter) and its divisions
of tenths and hundredths. It is far easier mental arithmetic to measure most
parts of a watch in a few millimeters and decimal fractions, than to use the
inch and thousandths. The latter usually requires use of odd figures in three
places, for sizes of watch parts.
Mexican agate - Any of many colorful varieties of agate, generally occurring in
smaller nodules than the Brazilian ones, but much more attractively banded and
not in need of the dyeing customary with Brazilian agates. Also, a misleading
term which has been applied to banded calcite or aragonite onyx, which, by
contrast, is often dyed.
Mexican black diamond - Misnomer for hematite.
Mexican diamond - Misnomer for rock crystal.
Mexican jade - A true jade, one of the few known occurrences of the mineral
jadeite, and extensively used by the pre-Colombian Mexican Indians. Apparently
found like the Burmese jadeite in loose boulders, but long known only in worked
objects. See MAYAITE and TUX-LITE. However, utmost caution should be observed in
the use of the term, for in recent years a calcite onyx-marble, dyed green, has
been widely sold in silver jewelry under the misleading name of "Mexican jade."
It is soft and easily scratched with a knife. It effervesces in hydrochloric
(muriatic acid), and is thus easily distinguished from the hard and insoluble
Mexican onyx - Banded yellowish, greenish calcite or aragonite commonly used in
ash trays and decorative objects. The Mexican onyx seen in the trade mostly
comes from Argentina.
Mexican opal - Precious opal mostly from Queretaro, Mexico. It is characterized
by a fine fire and an almost transparent body, which may be colorless, slightly
golden or slightly red, grading into FIRE OPAL with a strong body color and no
color play. It occurs in pockets in a reddish igneous rock, bits of which are
often polished with the stone.
Mexican pearl - Pearl from the Gulf of Mexico, supposed to be unusually larger
but less well-shaped and somewhat duller in color than oriental pearls. Also
called OCCIDENTAL PEARLS
Mexican turquoise - A misnomer; no important turquoise occurrence is known in
Mexico; probably intended for western U.S. turquoise. In general this material
is likely to be a little lighter and greener than much of the oriental, and to
have a brown-to-white matrix.
Mexican water opal - Mentioned by G. F. Herbert-Smith without definition, it
probably means the colorless transparent precious opal, characteristic of the
MI - Abbreviation for "moderately included." See CLARITY GRADE,
mica - (mike'a) A group of minerals, including several varieties known as
MUSCOVITE, BIOTITE, PHLOGOPITE, etc. They are important rock-making minerals
and have numerous industrial applications when found in large sheets. Hydrous
aluminum silicates with potash, iron, magnesia, etc., they are characterized by
a good cleavage, and great flexibility. LEPIDOLITE, a purple lithium mica often
associated with tourmaline, has been cut into decorative objects. FUCHSITE is a
muscovite with green coloring from chromium which gives aventurine quartz its
color. Some AGALMATOLITE is made of a fine-grained massive mica.
mi-concave - A form of watch glass or crystal, for open-face watches, in
cross-section appearing of uniform thickness throughout its "arch" with sloped,
straight-beveled sides to form clearance to fit in seat of bezel. One of the
oldest forms of watch crystals, but never entirely out of use as some other
forms have become.
micro-chronograph - A device used in connection with astronomical clocks, for
recording thousandths of a second.
microcline - (my'kro-kline) The tri clinic potash feldspar characteristic of
acid pegmatite dikes. It is often green, as well as pink, cream, and white. The
green variety is known as AMAZON STONE and is widely used as a decorative
material. The other varieties, more common, constitute most of the feldspar used
commercially in ceramics and scouring powders.
micrometer - A measuring instrument in which the object to be gauged rests on a
stationary block surface or "anvil" at one side, while against the other side is
brought up the end of a screw, which has a head graduated on its rim, from which
the measurement is read. With the screw-end against the anvil, the screw-head
graduation reads zero; as the screw is turned to open the space between anvil
and screw-end, each complete turn of the screw is indicated by graduation on a
tube ("sleeve") surrounding the screw, and subdivisions of each turn are
indicated by graduations on the "thimble" which acts as the screw head. All the
graduations are based on the pitch of the screwhead for the screw advances
lengthwise, per turn, exactly the distance between the tops of two adjacent
threads. Micrometer calipers are made in inches, thousandths and
ten-thousandths; and in metric measure in millimeters, tenths and hundredths.
The use of metric micrometers for watchwork is increasing. See METRIC
micrometer regulator - A regulator in a watch or portable clock, in which the
index-hand is moved by turning a screw instead of directly by pushing it with a tweezer, etc.
microminiaturization - The process and technique of producing machines or
devices to operate effectively in a fraction of the area formerly occupied.
micron - Unit of measurement, 1 millionth of a meter, or 1 thousandth of a
middle temperature error - In watches with bimetallic compensating balances and
steel hairsprings, even if adjusted to temperature so well that they would keep
time alike at the extremes of heat and cold, there will in all cases be a
gaining error at points of temperature between the extremes. This is due to a
difference in these two things: (1) the effect of changes of heat and cold on
the elasticity or "force" of the hairspring; and (2) the effect of changes of
heat and cold on the bending of the rim-segments of the compensating balance.
That is, the changes in hairspring and in balance, caused by temperature, do not
progress in both of them at the same rate, with the rise and fall of the
thermometer, so that perfect adjustment to all degrees of heat and cold is
impossible, and the middle temperature error is the result. Obviously with a
hairspring not much affected in timekeeping rate by temperature, compensation is
proportionately unnecessary, and middle temperature error practically
non-existent. These conditions are met commercially by the watches now being
made with hairsprings of alloy metals relatively unaffected by heat and cold,
midge stone - MOSS AGATE.
milk glass - Opaque glass in a milky-white color.
milk opal - Milky white common opal with which is associated the precious opal
in Australia and Hungary.
milky quartz - Opaque to translucent white coarsely crystalline quartz, commonly occurring in veins. Gold matrix specimens are usually composed of gold in
mill - Metal work. 1. A cutter for forming gear-teeth or other work, with
numerous teeth with profiles of the form to be produced, used on a rotating
spindle in an attachment to watchmakers lathe. 2. A pair of steel rolls to
rotate opposite to each other, used in jewelry shops for reducing thickness of
bars of metal.
Miller process - A method of refining gold by passing chlorine gas through the
molten metal. Base metals and silver are converted into chlorides which rise to
the top as fumes or slag.
millgraining - A detail of gem-stone setting, the formation of beading, or a set
of very small hemispheres in procession on the top of a knife-edge of metal in
the design of the setting. The beading is produced by a steel roller with
female beading sunk around its periphery, the roller set in a handle which
allows it to be pressed forcibly against the work, while advancing it along the
millgrain knurl - A millgrain wheel. See MILLGRAINING.
milliamperes - The thousandth part of an ampere.
millimeter - Unit of length measure, one thousandth of a meter. A millimeter is
.03937 inch. See METRIC MEASUREMENT.
mineral - A naturally occurring inorganic substance with fairly definite
physical properties and a chemical composition varying within certain limits.
mineralogy - The study of minerals.
mineral turquoise - A term sometimes used to accentuate the distinction between
TURQUOISE and ODONTOL1TE.
minute - 1. One-sixtieth of an hour of time. 2. One-sixtieth of a degree of arc.
minute-impulse relay - An electric relay for obtaining an instant change of
minutes in time-stamping clocks.
minute-jumper dial - On a watch or clock, a dial which has instead of a
graduated circle and hand, an opening in which appear numerals indicating
minutes, which are painted on discs rotating under the dial and moved by
minute pinion - In a dial train, the pinion fastened to the minute wheel which
wheel is turned by the cannon pinion; the leaves of the minute pinion engage the
teeth of the hour wheel. See DIAL TRAIN.
minute recorder, register - An attachment to a chronograph watch which indicates
on a dial the number of minutes during which the fifth seconds hands have run
between starting and stopping them for an observation.
minute repeater - A complicated watch which will strike time to the minute
whenever a slide on the case is pulled; the highest form of repeater. Less
elaborate mechanisms are repeaters that will strike the nearest quarter-hour;
or the nearest ten minutes after the hour.
minute track - The 60 markings in the ring around a timepiece dial.
minute wheel - In a dial train, the wheel with teeth engaging the leaves of the
cannon pinion, and with a pinion fastened to it which turns the hour wheel. See
miter gears - Bevel gears of equal diameters. S gears are used in some varieties
of stem wing and setting work.
mixed cut - A combination-type of cutting, crown being slightly higher and the table
larger than in a normal brilliant, and the pavilion step-cut, with the same number
facets as in the crown. The form is used to give the color obtained with the
step-cut some of the fire which is found in the brilliant cut. Fancy sapphires are
often cut in this style. See FRENCH CUT; BRILLIANT CUT; S CUT.
mobile - Horology. Generic term often applied to any and all of the parts of a
timepiece turn on the pivots, and more specifically, the arbors carrying wheels
mocha stone - MOSS AGATE.
mock pendulum - In old bracket clocks, a n disc on an arm of the actual pendulum
motions visible through an aperture in dial; to give a pleasing appearance of
"life the clock.
model - In jewelry, an original piece from which a mold is made to cast wax
patterns. May be made by "building up," as in making a piece of fine jewelry; by
"cutting down," making white metal models, or by carving building up in wax.
module - In wheelwork, the result of div: the pitch diameter by the number of
feet. A replaceable unit containing a group off as in electrical watches.
Moebius process - Method of refining silver tainting small amounts of gold.
Anodes of pure silver are electrolyzed in an acid silver nitrate bath; pure
silver is deposited on a cathode of sheet metal.
Moe diamond gauge - A gauge involving calipers and a table, designed by Charles
Moe for the determination of approximate weights of brilliant-cut diamonds.
Mogok - District in Upper Burma, which, since the 15th Century, has produced
rubies, including the best pigeon-blood red, besides spinel, sapphire, zircon
Mogok diamond - Local Indian name for colorless topaz.
Mohs' scale - A scale of relative hardness for use in testing minerals. Named
for the German mineralogist Friedrich Mohs (1772-1839), who proposed it in 1822.
The minerals are numbered, but the intervals between them are very different,
and diamond is far far harder than corundum, as much harder as corundum is than
talc. Minerals vary in hardness in different crystal directions, calcite for
example can be scratched by the finger nail on the face which truncates the
three cleavage rhombohedra. See WINCHELL HARDNESS SCALE.
Mojave moonstone - (mo-haav'ee) A gray translucent chalcedony, the name is used
to distinguish this from "blue moonstone," pale blue, and "California
moonstone," white. All these terms are misleading and undesirable.
mold - 1. A hollow form which gives shape to metal in its molten state.
costume jewelry, a fairly hard rubber form into which white metal is cast
directly. 3. A bronze or iron form into which metal is cast. 4. A separated
form made of sand or cuttlefish bone, into which metal is cast. 5. A flexible
rubber form into which casting wax is forced to make an expendable pattern. 6.
sectional, low-fusing metal form used for casting wax patterns of superior
dimensional stability. 7. A refractory form into which molten metal is forced
under pressure to produce intricate castings.
moldavite - (mole'dav-ite). A light green glass of natural but unexplained
origin. Originally thought to be volcanic glass, discoveries of the stone in
parts of the world where no volcanic activity has recently occurred, have led to
the theory that they represent meteoritic glass. Moldavite is found along the
Moldau in Bohemia, hence its name. It is also known under many erroneous or
misleading names such as Bohemian chrysolite, bottle stone, chrysolite,
pseudochrysolite, false chrysolite, or water chrysolite.
molding - See CASTING.
mold frame - A metal block with an opening the size of the desired mold. Into
this opening rubber is vulcanized around a metal model to form the rubber mold.
mold mark - A seam on a piece of glassware, indicating the piece was formed in
a mold. When the piece is well finished, the mark should not be obtrusive.
mold rubber - A highly flexible latex rubber used in making rubber molds.
Vulcanizes at approximately 300°F.
mole-stone - Ancient, perhaps Roman, glass bead found in the earth and believed
by the superstitious to have certain magical properties. Toadstone, snail-stone
and adder-stones were the same.
molochites - Ancient name for green jasper.
molybdenum bi-sulphide, di-sulphide - A soft graphite-like mineral used as a
lubricant in watches and clocks.
monazite - A Bolivian variety of this rare earth phosphate looks pink under
incandescent light, dark green in daylight or fluorescent light; not found in
Monel metal - A tough nickel-copper alloy gray in color. Melting point: 2370°F.
monitor lathe - Lathe with revolving slide rest multiple tool-holder, for
turning successively a variety of forms on one piece of work; the basic
principle of nearly all machines used in watch and clock factories in
mass-production of parts for timepieces.
monochromatic - (mo'no-kro-matt"ik) Of a single color. A monochromator is
actually a sort of spectroscope so designed that only a narrow band of light of
one or another wave-length (hence color) is emitted at any one time. Useful in
gem testing when sodium light wavelengths are needed, or some other standard
monoclinic - A crystal system, in which there are three unequal axes, two of
which are at right angles to each other, and the third inclined to the plane of
the other two. Diopside, epidote, spodumene and sphene crystallize in this
monometallic balance - A watch balance made of one metal throughout, used in
combination with a hairspring of alloy metal in which there are practically no
changes of elastic force under changing conditions of heat and cold. A
monometallic balance does not compensate because with its hairspring
compensation is not needed. See BI-METALLIC BALANCE; COMPENSATION; MIDDLE TEMPERATURE ERROR.
monster-pearl - Round pearl of exceptional size, also known as a paragon.
Montana jet - Obsidian.
Montana ruby - An infrequent hue in the Montana sapphires, but some are red
enough to be accepted, especially locally, as rubies.
Montana sapphire - In trade terminology, a Montana sapphire is a blue sapphire
which is lighter and more steely in color than the Kashmir and Ceylonese.
However, many fancy-colored sapphires are found in Montana and there might be
some danger of confusion by the use of Montana as a geographical modifier as
well as a descriptive adjective.
Mont Blanc ruby - Misnomer for a reddish quartz. See RUBASSE.
Montgomery dial - A design of watch dial, especially for railroad watches, with
numerals representing each minute, outside the minute-circle, and very bold
hour-numerals; intended to aid quick and exact reading of time; introduced by
Chief Time Inspector Montgomery of the Atchison Topeka and Santa FeR. R. about
Moor's head - Term applied to black colored tourmalines from Elba.
morganite - Pink caesium-bearing beryl, named by G. F. Kunz in honor of J. P.
Morgan. Found in California, Brazil and Madagascar.
morion - An old term for very dark, almost black, smoky quartz.
moro - Japanese oxblood red coral.
moroxite - A name originally applied to greenish blue apatite crystals from
Arendal, Norway, in reference to their shape, the terminations of which were
blunt. Its use has been extended quite unwarrantedly to cover any bluish
apatite, regardless of the crystal habit, and most "moroxite" today is of
Canadian origin, though little is of gem quality.
morse - A clasp or brooch used to fasten an ecclesiastic cope.
mosaic - Jewelry. Decorative art work, usually of Italian origin, in which a
design or picture is formed of bits of colored stone or enamel inlaid in
cement, with their flat tops set or ground flush with the surface of the work.
mosaic gold - Karat gold, the surface of which is composed of fragments of red,
yellow, green and white gold, in random pattern.
moss agate - A cryptocrystalline variety of quartz, with stains of various types
and colors, giving rise to moss, fern or treelike patterns. The black stains are
caused by manganese oxide, reds and greens are probably iron. The Montana moss
agates are characteristically light yellow, almost white, with black dendritic
patterns in them; moss agates from other localities are very different; the
well-known Indian moss agate is green.
moss jasper - Name given to a cabochon quartz variety found in the Arizona
petrified wood, in which there are bands of opaque-colored jasper with streaks
of translucent chalcedony.
moss opal - Opal with markings like moss agate.
mother of emerald - Misnomer for PRASE.
mother of pearl - The iridescent pearly lining of a shell.
motion - Horology. Term used to denote the angular extent of motion of a watch
balance or rarely of a clock pendulum, as "a good motion," "a poor motion,"
meaning respectively sufficient or insufficient angular amount of rotation in
the action of a timepiece balance. See ARCS.
motion work - Term customarily used in Europe to denote the dial-train of watch
or clock. See DIAL-TRAIN.
motor barrel - A watch mainspring barrel designed so that the mainwheel, with
teeth engaging the center pinion, turns on the barrel arbor pivots as the watch
runs. The other principal type of mainspring barrel in modern watches is the
motor-wound clock - A type of electric clock in which there is the conventional
train, escapement and balance or pendulum, but in which the mainspring is
automatically wound whenever necessary by an electric motor.
mottled stone - Stone with patches of color, not uniform.
mount - A general term to include the metal base, molding, rim, cover clamp, or
other accessory by which a utensil of silver, pottery, glass, or
other material is decorated and adapted for use.
mountain mahogany - Red OBSIDIAN.
mounting - 1. A piece of jewelry made for stones, complete except for the
setting of the stones; ideally designed to bring out the beauty of the stone,
secure the stone against loss or damage, and produce a pleasing, well-balanced
whole; "an unmounted piece." 2. Setting or fastening of stones in place is
sometimes referred to as "mounting the stones."
movement - The mechanism of a watch or clock, as distinguished from the case.
movement cover - A glass dome used on watchmakers' benches, to cover partly
completed watches to keep dust off them.
movement holder - 1. A device for holding watch movements during assembly or
other work, either a set of blocks with recessed shoulders in the top to hold
the movement, one block for each size and shape of movement; or an adjustable
clamp device used for many different movement forms. 2. A rack holding a number
of watch movements, with hinges so that it may be clamped in various positions,
used in watch factories for timing watches while adjusting them to positions.
Mtoroite - A prase-like, deep spinach green chalcedony, somewhat less
translucent than chrysoprase, from Mtoro, Rhodesia.
muddy stone - A dull stone, due to lack of complete transparency.
Mueller's glass - Clear colorless hyalite opal.
muffle furnace - A gas blast furnace with a muffle inside, which is a box made
of fireclay or similar material, usually removable for charging and removing
work. In horology, muffle furnaces are used for hardening steel; in jewelry
shops for enameling etc. There are also furnaces designed for combined use as
muffle furnace or crucible furnace, the latter for melting metals in a crucible.
multimeter - An electrical meter capable of measuring volts, amperes, ohms,
multiple case - One of a class of watch cases in which there are more than one
separable cases used together. Examples are the pair-case (double); the triple
case with an outer case to protect the decorations of the outside one of a pair
case; and reversible combination open-face with hunting case watches.
multiplexing - In electronic timepieces, the sophisticated integration of
various electronic functions in a small (circuit) area, allowing complex
functions in a small watch.
Mumetal - A nickel, iron, copper alloy with high magnetic permeability, used as
cores in magnetic balances, pendulums.
muriatic acid - Popular name for hydrochloric acid, which is an aqueous solution
of hydrogen chloride gas, used in jewelry work mixed with nitric acid to make
aqua regia, for dissolving precious metals; and in horology for making
blue-removing solution. See AQUA REGIA; BLUE REMOVER.
muscle pearls - Small distorted pearls found near the muscle of the oyster.
mushroom stud - A hairspring stud shaped like a' button on a stalk; contained by
a cap on the balance bridge pier.
mussel egg - Tennessee name for a fresh water pearl.
mutton fat jade - A pure limpid white variety of nephrite.
Mutzschen diamonds - Misnomer for rock crystal.
myrickite - Common opal or chalcedony with inclusions of bright red cinnabar,
the mercury ore. The opal variety is also known as "opalite." Found in the west
in most mercury regions.
Mytilus pearls - (mit'til-lus) Pearls from the Mytilus or common mussel.