Gemmology
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Tuesday, 21 February 2017


Gemmology — gemstones — characteristics, classification, specimens, library
Chromian diopside

GEMMOLOGY — GEMSTONES

characteristics, classification, specimens, library

As gemstones we accept cut specimens of crystals of natural mineral species having a visible transparency and certain durability. From over 4800 known minerals (according to data of the International Mineralogical Association), approximately 150 satisfy the above conditions and form crystals of sufficient size to be cut.

The section ‘Classification’ presents descriptions of 162 different kinds of natural gemstones (104 mineral species). The Nickel-Strunz systematic order (10th edition) is used. Since gemmology does not always follow the systematics of minerals in naming, many popular varieties or just ’names’ are listed.

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Classification
Featured

Actinolite

— Produced by regional or contact metamorphism of magnesium carbonate, mafic, or ultramafic rocks (Anthony et al., 2001—2005). Faceted specimens are extremely rare.
Actinolite

The section ‘Repository’ contains data and photos of 670 specimens of gemstones. The smallest is just 1.96 mm (0.02 ct) ruby from Mozambique, and the largest — 70.11 mm (326.60 ct) rock crystal from Africa. Besides there are 7 specimens of synthetic stones.

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Repository
Topaz — specimen 0500

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Benitoite — specimen 0248
Topaz — specimen 0253
Marialite-meionite series — specimen 0255
Sapphire — specimen 0263

— More from ‘Repository

Currently there are 279 bibliographical references and abstracts to publications with gemmological or mineralogical thematics in the ‘Library’. The section comprises also a glossary with 380 terms.
Library
Glossary

olivine — a series between forsterite and fayalite
oolite — (egg stone); a sedimentary rock formed from spherical grains composed of concentric layers
opal — species of mineral; see Opal in ‘Classification’
opalescence — a type of dichroism seen in opals; gems appear yellowish-red in transmitted light and blue in the scattered light perpendicular to the transmitted light
Publications

von Leonhard, K. C., 1821 — Scheelit — Published in 1821 in ‘Handbuch der Oryktognosie’; contains the original description of the mineral scheelite.
Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Uvite — Features the data of uvite; from ‘Handbook of Mineralogy’.