Gemmology
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Classification

Kornerupine
Kornerupine

— In boron-rich igneous and sedimentary rocks; in metamorphosed anorthosite complexes (Anthony et al., 2001—2005).

Specimen figured

Kornerupine — specimen 0104weight: 1.35 ct; shape: oval. Very clean specimen; good mixed style cut. Source: Michael Asa, Gem Line Inc.

Classification


The section ‘Classification’ presents descriptions of 163 different kinds of natural gemstones (104 mineral species). The Nickel-Strunz systematic order (10th edition) is used. Specimens of the classes shown below are currently available. Since gemmology does not always follow the systematics of minerals in naming, many popular varieties or just ’names’ are also listed.

Classes after Nickel-Strunz

1. Elements
2. Sulphides & sulphosalts
3. Halides
4. Oxides & hydroxides
5. Carbonates (Nitrates)
6. Borates
7. Sulphates
8. Phosphates, arsenates, vanadates
9. Silicates


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).

Specimen figured

Cerussite — specimen 0029weight: 3.71 ct; shape: octagon. Very clean specimen; very good step cut style. Source: John Bradshaw, Coast to Coast Rare Stones International.
Cerussite — specimen 0029