Gemmology
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Sunday, 16 December 2018


Gemmology — gemstones — characteristics, classification, specimens, library
Rhodolite

GEMMOLOGY — GEMSTONES

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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Classification
Featured

Cordierite

— In thermally metamorphosed argillaceous sediments and regionally metamorphosed schists, gneisses; in mafic igneous rocks and granites (Anthony et al., 2001—2005). The gemstone bears the name iolite.
Cordierite

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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Repository
Prasiolite — specimen 0421

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Hambergite — specimen 0487
Hyacinth — specimen 0488
Hambergite — specimen 0489
Phenakite — specimen 0490

— 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.
Library
Glossary

opal — species of mineral; see Opal in ‘Classification’
opalescence — a type of dichroism seen in opals; gems appear yellowish-red in transmitted light and blue in the scattered light perpendicular to the transmitted light
opaque — clarity grade in gemstones; does not allow light to pass through, highly included; some gems are naturally opaque
Oregon sunstone — variety from anorthite-albite series; see Oregon sunstone in ‘Classification’
Publications

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