Emerald Doublet
Photo by YourGemologist
General Information
What color is it?: Green...well, sort of. Depending on how you look at it. As shown in the photograph below it can turn colorless if you look at it from the side. But basically they are a nice emerald green.
What is the story behind this gemstone?: These types of gemstones have been on the market for many decades. But somehow they keep showing up. The above example is being currently produced by the Lannyte Company who makes many types of synthetic and imitation gemstones. They are composed of layers of natural green emerald and clear glass. But together to form what we call an assembled stone. Some gemologists get the creeps when it comes to these, only because they don't know how to use any other piece of equipment than a refractometer. And while at the Tucson Gem Show I understand one G.G. even let the guys in the Lannyte booth have it because of how difficult it would be to identify if someone set it in a bezel setting where you could not see the glass center. (Since the top is emerald it would test out as an emerald) Unfortunately, the Graduate Gemologist did not consider that it is near impossible to make one of these stones without leaving some tell-tale gas bubbles. Which this one did, and I would venture a guess that all the others do also. But it is a viable alternative to an expensive natural emerald, and the Lannyte Company is very forth coming about assisting gemologists with the proper identification of their products. So no gemologist should get to freaked about this stone. They have been around for many, many years, and should not pose a problem to an experienced gemologist.
Here's the rest of the story on the emerald doublet......
Chemical: Si02 (silicon glass) and BeAlSiO2 for the emerald.
Formation: Three layers....two emerald and one glass literally glued together.
Crystal System: Hexagonal in general due to emerald
Unusual Properties: Turn it side ways and it gets a clear line running through it.
RI: 1.577 - 1.583 (same as the emerald on top)
Optical Character: U-
Hardness: 7.5 - 8
Specific Gravity: 2.72 + -
Special Identification Properties: Easy to identify due to colorless center and gas bubbles.
Gemological Identification
Primary Test: Inspection with a 10x loupe and light source
The
clear glass middle section as seen in 10x through the girdle
Diagnostic
gas bubbles shown under 30x with dark field illumination
Gas
bubbles visible in 10x magnification using fluorescent lighting.
Secondary Test: None needed if you own a loupe.
With greatest appreciation to:
Synthetic Imitation & Treated Gemstones by Michael O'Donoghue, Butterworth Heinemann, London, 1997, and
Gems Made by Man, Kurt Nassau, Gemological Institute of America, Santa Monica, 1980
Without whose excellent books
on this subject these web pages would not be possible. YourGemologist.com
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