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Friday, 19 January 2018

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


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 164 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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— Most common in felsic volcanic rocks; in volcanic glass; also from mafic, high-temperature contact metamorphic, and hydrothermally altered rocks; from eclogite nodules in kimberlite (Anthony et al., 2001—2005).

The section ‘Repository’ contains data and photos of 732 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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Dravite — specimen 0536

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Rose quartz — specimen 0079
Petschite — specimen 0081
Petschite — specimen 0082
Friedelite — specimen 0086

— 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 383 terms.

londonite — species of mineral; faceted specimens exist
lozenge — a shape in faceting a gemstone
mafic — an adjective describing a silicate mineral or rock that is rich in magnesium and iron
magma — a molten rock found beneath the surface of the Earth

Dana, E. S., 1888 — Preliminary notice of Beryllonite, a new mineral — Published in 1888 in ‘American Journal of Science’; contains the original description of the mineral beryllonite.
Volborth, A., Stradner, E., 1954 — Väyrynenit BeMn[PO4](OH), ein neues Mineral — Published in 1954 in ‘Anzeiger der Österreichischen Akademie der Wissenschaften’; contains the original description of the mineral väyrynenite.