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Tuesday, 24 October 2017

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 163 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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— Common in the oxidised zone of lead deposits, where it may constitute an important ore (Anthony et al., 2001—2005). Faceted specimens are very rare. The largest faceted stone is a 408 carat from Tsumeb, Namibia (Arem, 1987: 64).

The section ‘Repository’ contains data and photos of 728 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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Spinel — specimen 0496

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Colour change garnet — specimen 0272
Pargasite — specimen 0275
Ruby — specimen 0276
Bytownite — specimen 0284

— 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 381 terms.

igneous rock — one of the three main rock types; formed through the cooling and solidification of magma or lava
ilmenite — species of mineral; faceted specimens exist
ilvaite — species of mineral; faceted specimens exist
indicolite — variety of elbaite; see indicolite in ‘Classification’

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.
Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Triplite — Features the data of triplite; from ‘Handbook of Mineralogy’.