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Synthetic
Moissanite
Y2K in a gemstone! Do we need to panic? People are getting all hyped up about moissanite. By now we should all be aware that it tests as diamond using conventional diamond thermal probes, but this is not the end of the world, as we know it, a little care and caution are called for. The manufacturers, C3, gave the trade enough warning before putting it out for sale. They even developed their own tester to separate moissanite from diamond. Trade magazines have been running articles on it for eighteen months or more. We bought a piece to have as a test stone at the Tucson gem show a year ago. And finally it arrived. In mid-January 1999, a number of pieces showed up in Toronto at pawnshops and second hand dealers, precisely the people without the gemmological expertise to protect themselves. And sure enough, some of them were hurt. As soon as moissanite hit the market, we issued a lab alert. We made the trade press aware and sent out as many notices as possible. There were seminars held and lectures given on how to identify it. Now, many months later, the major portion of a sample of jewellers, commonly in the business of buying diamonds from the public, have been fooled by a ring set with moissanite! It should not be that difficult to identify!!!
You do not have to own a piece of expensive technology to identify moissanite, just a 10X loupe and good lighting. The table below is a comparison of diamond and the two major simulants, cubic zirconia (CZ) and moissanite. The dispersion of moissanite
is twice that of diamond, making the stone much more firey. The hardness
(resitance to scratching) of 9.25 is measured on a scale that is not
abosolute. In fact, diamond is many orders of magnitude harder than
any other gem, natural or created.
Almost all diamond simulants share one property with diamond. They are singly refractive. The term, singly refractive means that a ray of light passing through the gem is slowed but otherwise unaffected by the medium. Glass is a singly refractive material, as are cubic zirconia, garnet and diamond itself. Synthetic moissanite, is doubly refractive. This means that a ray of light passing through this sort of gem is slowed, bent and split in two as it passes though the medium. Sapphire is a doubly refractive material, as are peridot, tourmaline and zircon. The effect of double refraction
becomes visible, for example in peridot or zircon, when the back facets
of the stone are viewed through the table. There seem to be two of every
facet and the culet. This effect is called doubling.
Therefore, when examining a
"diamond" after testing it with the thermal probe, tilt the stone slightly
and look at the culet and the other pavilion facets through one of the
crown facets other than the table. No doubling, it's a diamond. If you
see doubling it is not a diamond.
The facetted moissanite we have seen is quite yellow (K and lower) in colour and it (sometimes) may have inclusions (whitish, VS and lower in appearance). It is now also cut in princess and radiant cuts as well as round. It is the kind of gem that one would not think twice about, it has to be diamond: it has colour, it may have marks. Well, what you have to do now is look just a bit more carefully at the stone you are accepting for repair or appraisal. Before you write diamond on the job bag or take-in form don't simply use the diamond probe. Look at it too. If there is apparent doubling seen through the crown facets, or of you are unsure about what you are seeing, please call, send or bring it in, we will be happy to identify the stone for you (fees may apply). If you need more information please call Harold Weinstein Ltd. at: 416.366.6518. |
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