Diamonds:Gemology

The conventional thermal probe separates diamond from all simulants except moissanite. A new tester finishes the job

Retailers who fear the new diamond simulant moissanite might pass through their hands undetected can breathe a sigh of relief. The company that created the simulant has created a device to detect it.

The $525 Tester Model 590 was designed to easily and quickly distinguish synthetic moissanite from diamonds, says Jeff Hunter, CEO of C3 Inc., creator of the diamond simulant and the testing device. "Our intention is to fully prepare the jewelry industry for the introduction of lab-created moissanite," he says.

Conventional diamond testers check for thermal conductivity and are useful in separating diamond from simulants such as cubic zirconia, corundum, glass, synthetic rutile and zircon. But they are useless in separating diamond and moissanite because both are thermally conductive.

Moissanite, a silicon carbide that is rare as a natural stone, is now available as a lab-grown product in small sizes (less than 0.05 carat). Bigger stones are expected from C3 later this year. It can be distinguished from diamond by other standard, albeit more time-consuming, gemological means. For example:

• Moissanite is doubly refractive; diamond is not.
• Moissanite has a lower specific gravity than diamond (moissanite floats in 3.32 specific gravity liquid).
• Under magnification, moissanite doesn't exhibit "bearding" or "naturals." Bearding, minute fissures in a diamond's girdle, occur in the cutting process. Naturals are growth characteristics in a diamond. (Note: the absence of bearding and naturals does not separate moissanite from other diamond simulants, and not all diamonds exhibit bearding.)

Tester Model 590 distinguishes diamonds from the new simulant moissanite. C3 Inc., P.O. Box 13533, Research Triangle Park, NC 27709-3533; (919) 468-0399.

by Robert Weldon, G.G.

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