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Wednesday, 8 April 2020

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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Chrysoprase — specimen 0465

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Spinel — specimen 0041
Milky quartz — specimen 0042
Indicolite — specimen 0043
Milky quartz — specimen 0044

— 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.

tuff — a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption
turquoise — species of mineral; see turquoise in ‘Classification’
ultramafic rock — igneous and meta-igneous rock with a very low silica content (less than 45%), composed of usually greater than 90% mafic minerals
umbalite — a synonym of rhodolite; mined in Umba Valley, Tanzania

Haidinger, W., 1828 — On Herderite, a new Mineral Species — Published in 1828 in ‘The Philosophical Magazine’; contains the original description of the mineral herderite.
Breithaupt, J. F. A., 1818 — Gattung B. Amblygonit — Published in 1818 in ‘Handbuch der Mineralogie von C. A. S. Hoffmann’; contains the original description of the mineral amblygonite.