Gemmology
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Triplite

Class: Phosphates, arsenates, vanadates
Group: Triplite

A principal primary phosphate, or replacing earlier species, in complex zoned granite pegmatites; in hydrothermal tin veins (Anthony et al., 2001—2005). One of the rarest gemstones.
Triplite — specimen 0587
Triplite — specimen 0587, photo © NMNHS

Original description: ‘Triplit’ Hausmann, J. F. L., 1813. Triplit — Handbuch der Mineralogie, Göttingen: 1079—1080 [view in ‘Library’].

Type locality: Chanteloube, Razès, Haute-Vienne, Limousin, France.

Type material: unknown.

Etymology: from the Greek word τριπλόος (triplos), threefold, for its cleavage.

Distribution: some prominent occurrences: Canada: Nova Scotia, East Kemptville tin mine; France: Haute-Vienne, near Chanteloube; Germany: Bavaria, Hagendorf; USA: Maine, Oxford Co., Stoneham (Anthony et al., 2001—2005). Facetable material known from Pakistan, Gilgit-Baltistan, Baltistan, Skardu.

Chemistry

(Mn2+,Fe2+,Mg,Ca)2(PO4)(F,OH)

Essential elements: hydrogen (H), oxygen (O), fluorine (F), magnesium (Mg), phosphorus (P), calcium (Ca), manganese (Mn), iron (Fe).

Crystal data

Crystallography: monoclinic — prismatic. Crystal habit: crystals are typically very rough, but may have many indistinct forms, to 4 m; usually nodular, massive (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {001}, good; on {010}, fair; on {100}, poor (Anthony et al., 2001—2005). Fracture: uneven to conchoidal (Anthony et al., 2001—2005). Tenacity: no data. Hardness: 5—5.5 (Lazzarelli, 2012). Density: 3.85—3.94 g/cm3 (Lazzarelli, 2012). Luminescence: none. Other: soluble in acids.

Optical properties

Colour: chestnut-brown, reddish brown, flesh-red, salmon-pink; brownish black to black if altered; in transmitted light, pale brownish yellow to dark reddish brown (Anthony et al., 2001—2005). Diaphaneity: transparent to opaque (Anthony et al., 2001—2005). Lustre: vitreous to resinous (Anthony et al., 2001—2005). Refractive index: 1.643—1.703 — anisotropic [biaxial (+)] (Lazzarelli, 2012). Birefringence: 0.02. Dispersion: moderate to strong (Anthony et al., 2001—2005). Pleochroism: distinct; yellow-brown to reddish brown (Anthony et al., 2001—2005).

Material from ‘Repository’

1 specimen: 0587 — 0.11 ct, Pakistan, Gilgit-Baltistan (Northern Areas), Baltistan, Skardu District.


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