Gemstones of the World: Newly Revised Fifth Edition

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Feldspar is prized for its billowy blue adularescence, caused by light scattering from an intergrowth of microscopic, alternating layers. Moh’s scale of hardness, basic mineral chemistry, specific gravity, cleavage and fracture, refraction and absorption, pleochroism, and fluorescence are described in sections followed by charts of these properties for selected gemstones. Aquamarine is often heated to remove yellow tones, or to change green colors into the more desirable blue, or enhance its existing blue color to a deeper blue.

List of Gemstones: Precious and Semi-Precious Stones - Gem

If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. Rare or unusual gemstones, generally understood to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and red beryl. Synthetic gemstones share chemical and physical properties with natural gemstones but there are some slight differences that can be used to discern synthetic from real.In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. Their ranks include the world’s most famous jewel—the Hope—and the most expensive gem ever auctioned—The Graff Pink. To minimize such differences, seven of the most respected labs, AGTA-GTL (New York), CISGEM (Milano), GAAJ-ZENHOKYO (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), for the standardization of wording reports, promotion of certain analytical methods and interpretation of results.

List of individual gemstones - Wikipedia List of individual gemstones - Wikipedia

Group of precious and semiprecious stones—both uncut and faceted—including ( clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster.Determining a "country of origin" is thus much more difficult than determining other aspects of a gem (such as cut, clarity, etc. Each entry offers complete information on a stone's formation and structure; physical properties and characteristics; and methods of working, cutting, and polishing.