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Thursday, 25 April 2019

Gemmology — gemstones — characteristics, classification, specimens, library


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 171 different kinds of natural gemstones (106 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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— Also known as sphene; a common accessory mineral in intermediate and felsic rocks, pegmatites, and alpine veins; in gneisses, schists, and some skarns (Anthony et al., 2001—2005).

The section ‘Repository’ contains data and photos of 760 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 8 specimens of synthetic stones.

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Amethyst — specimen 0703

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Grossular-andradite series — specimen 0027
Andalusite — specimen 0033
Oregon sunstone — specimen 0038
Spinel — specimen 0041

— More from ‘Repository

Currently there are 283 bibliographical references and abstracts to publications with gemmological or mineralogical thematics in the ‘Library’. The section comprises also a glossary with 391 terms.

peridot — variety of forsterite; see peridot in ‘Classification’
peridotite — a dense, coarse-grained igneous rock, consisting mostly of olivine and pyroxene
petalite — species of mineral; see petalite in ‘Classification’
petschite — variety from marialite-meionite series; see petschite in ‘Classification’

Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Clinozoisite — Features the data of clinozoisite; from ‘Handbook of Mineralogy’.
Weinschenk, E., 1896 — Ueber Epidot und Zoisit — Published in 1896 in ‘Zeitschrift für Kristallographie’; contains the original description of the mineral clinozoisite.