Gemmology
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Wednesday, 24 October 2018


Gemmology — gemstones — characteristics, classification, specimens, library
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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

Cerussite

— 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).
Cerussite

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
Rhodolite — specimen 0653

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Rock crystal — specimen 0616
Rainbow obsidian — specimen 0617
Agate — specimen 0619
Agate — specimen 0620

— 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

clay — mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure
cleiophane — old name for a light-coloured sphalerite; see cleiophane in ‘Classification’
clinochlore — species of mineral; data
clinohumite — species of mineral; see clinohumite in ‘Classification’
Publications

Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Gedrite — Features the data of gedrite; from ‘Handbook of Mineralogy’.
Lazzarelli, H. N., 2012 — Gemstones Identification. Blue Chart — A compilation of key information to analyse the results obtained with standard gemological tools such as refractometer, microscope and loupe, dichroscope, polariscope, etc.