Gemmology
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Classification

Andalusite
Andalusite

— A result of contact metamorphism of argillaceous sediments, also in regionally metamorphosed schists. Rare in granites and pegmatites (Anthony et al., 2001—2005).

Specimen figured

Andalusite — specimen 0034weight: 0.55 ct; shape: round. Very clean specimen; very good mixed style cut. Source: John Bradshaw, Coast to Coast Rare Stones International.

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
Gadolinite-(Y)

— In granite and alkalic granite pegmatites (Anthony et al., 2001—2005). Faceted specimens are extremely rare.

Specimen figured

Gadolinite-(Y) — specimen 0087weight: 2.21 ct; shape: octagon. Clean, opaque specimen; very good step cut style. Source: John Bradshaw, Coast to Coast Rare Stones International.
Gadolinite-(Y) — specimen 0087