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.
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).
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, 35.3°N 75.61667°E.
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