[Jewelry making - Article 00184] - Re: [Orchid] Lapis grading system?

[leonid Surpin]

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    The transparency of the diamond can be understood as transparency of
    the water. 

    If we fill a glass of water from pristine mountain stream and
    compare it side by side with the glass of water from the tap, the
    difference can be seen. 

    The will be on other material visible but 2 glasses will look
    different. 

    In diamond it can be explained by how well the crystalline structure
    was formed. We know that diamond crystallizes in the cubic system,
    but in process of formation there could be slight defects in the
    crystalline structure. These defects, not visible even under
    relatively high magnification, will interfere this the passage of
    light and render diamonds less transparent to a different degree in
    different diamonds. If diamond comes from geological deposit which
    formed slowly the crystal structure would be more approaching ideal
    and therefore more transparent to light. Golconda mines were such a
    slow formed geological deposit. It is not likely that one can
    encounter Golconda diamond, but to judge "water" in general,
    submerge diamonds in liquid with refractive index approaching
    diamond's and compare the degree of visibility. The one less visible
    will be the one with higher transparency. Even distilled water can be
    used, but of course with less accuracy. 

    There is a book. The title is Romance of The Golconda Diamonds or
    something similar. I even think I saw it on GIA website bookstore. It
    should provide more information on the subject. 

Leonid Surpin
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