This gemological tool is helpful with identifying certain red, blue and green gemstones. It is used to determine whether a gemstone is natural or synthetic and can also be used for detecting aquamarine, blue topaz and their synthetic blue spinel simulants as well as for detecting dyes in certain gemstones. The filter is designed to only transmit deep red and yellow-green light. So for example when looking at synthetic blue spinels, they should appear yellowish-orange or pink while the stones they simulate, aquamarine and sapphire appear green or greenish gray. This along with a dichroscope are powerful tools in examining gemstones.
To use: Hold the filter close to the eye while using a strong electric light (incandescent preferably, not LED), The stone may appear to change color. When examining the filter must be held near the eye but does not need to be very close to the stones, but good light is important.
- Chelsea filters transmit deep-red light (690nm) and yellow-green light (570nm) which is used to help identify gemstones
- Commonly used on emeralds, aquamarine, blue topaz and synthetic spinel
- Filter is contained in a flip-out case to protect the lens
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