[Jewelry making - Article 00408] - Re: [Orchid] International Gemological Institute's certificates

[Richard W. Wise]

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    I am not familiar specifically with IGI's colored stone certificates.
    But, here are some guidelines to follow when you look at any lab
    cert. Each lab has its methodology, prejudices, strengths and
    weaknesses. This is simply because the trade has managed to keep the
    principles of quality grading gemstones a secret even from
    themselves. Lab gemologists come from different traditions with
    differing approaches and opinions. Dealers are well aware of this and
    tend to exploit it, that is, they will send a stone to a lab that is
    likely to give the best cert to a particular stone. So if you are
    dealing with, say a padparadscha sapphire, labs have different
    definitions and the dealer will send the stone to the lab whose
    definition his stone fits. 

    Votaire said: If you would speak with me, define your terms. Until
    recently labs did not even use a standard terminology and in the
    trade dealers use various terms some of which are simply inaccurate.
    There is beginning to be a generally accepted terminology for
    describing color. GIA's new colored stone course does follow that
    terminology and by doing so has moved the standardization process
    forward. 

    There is still no generally accepted explicite colored stone grading
    system although I contend there is certainly an implicte one that
    exists in the marketplace. I have tried to make the princples of this
    system explicite in my book. 

Richard
http://www.rwwise.com
For Information and sample chapters from my new book: 
www.secretsofthegemtrade.com

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