[Jewelry making - Article 00371] - Re: [Orchid] Red amethyst?

[leonid surpin]

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>     Not sure gemmological laboratories would appreciate your first
>     sentence. There are ways to test natural v. synthetic amethyst. Not
>     always easy granted, but inclusions in some stones (nail-heads,
>     colour zoning, Brazil-law twinning and ultimately FTIR
>     spectrometery will usually get most these days. 

    Yes, there are ways, but Amethyst presents a special problem. 

    Inclusions do not help unless they are present. Amethyst is
    frequently clear and we really perfected quartz synthesis so
    synthetic crystals do not have tell-tale signs. Brazil-law twinning
    worked for a while, but now twinned crystals easily synthesized, so
    it is not a proof anymore. Since amethyst colour is naturally
    radiation induced and natural and synthetic gems are virtually
    identical it is impractical ( while theoretically possible ) to use
    sophisticated testing due to high cost of testing and relatively low
    cost of amethyst. This is exactly why when Brazil-law was no longer a
    conclusive test, the price of the Amethyst collapsed. The gem would
    cost much more is identification was commercially feasible. 

    There are indication that one can use but the interpretations are
    subjective and depend on individual colour perception. Difference in
    pleochroism colour range exist, and colour distribution in natural
    amethyst is differs from synthetics. In natural amethyst colour is
    restricted to grows zones associated with rhombohedral facets. Grows
    zones associated with pyramidal facets are colour free and have
    different degrees of transparency. If crystal is twinned, ( and most
    of them are ) the colour scheme is even more complex. Synthetics do
    not exhibit such colour distribution, but it is not easily detected
    and therefore is of little practical value. 

Leonid Surpin.
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