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Monday, 19 March 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 172 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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— A rare accessory mineral formed in boron-rich skarns at the contact of limestones with granite or gneiss (Anthony et al., 2001—2005). Faceted specimens are relatively rare. The largest faceted stone is a 158 carat from Sri Lanka (Arem, 1987: 173).

The section ‘Repository’ contains data and photos of 745 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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Verdelite — specimen 0535

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Andalusite — specimen 0033
Oregon sunstone — specimen 0038
Spinel — specimen 0041
Milky quartz — specimen 0042

— 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 392 terms.

lazulite — species of mineral; see lazulite in ‘Classification’
lazurite — variety of haüyne; constituent of lapis lazuli; see lazurite in ‘Classification’
leucite — species of mineral; see leucite in ‘Classification’
limestone — a sedimentary rock composed largely of the minerals calcite and aragonite

Rose, G., 1823 — Ueber den Feldspath, Albit, Labrador und Anorthit — Published in 1823 in ‘Annalen der Physik und der Physikalischen Chemie’; contains the original description of the mineral anorthite.
Shepard, C. U., 1839 — Notice of Danburite, a new Mineral Species — Published in 1839 in ‘American Journal of Science and Arts’; contains the original description of the mineral danburite.