Painite

Painite
Painite from Myanmar, 2 cm long
General
Category Borate minerals
Formula
(repeating unit)		 CaZrAl9O15(BO3)
Strunz classification 6.AB.85
Dana classification 7.5.2.1
Crystal system Hexagonal[1]
Crystal class Dipyramidal (6/m)
(same H-M symbol), although earlier reported as hexagonal (6)[2]
Space group P63/m
Unit cell a = 8.72 Å,
c = 8.46 Å; Z = 2
Identification
Color Red, brownish, orange-red
Crystal habit Elongated crystals, pseudo-orthorhombic[3][2]
Mohs scale hardness 8
Luster Vitreous
Streak White
Diaphaneity Transparent
Specific gravity 4.01
Optical properties Uniaxial (-)
Refractive index no = 1.8159, ne = 1.7875[3]
Pleochroism

Ruby-red parallel to [0001]; pale brownish orange or pale

red-orange at right angles to [0001]
Solubility Insoluble in acids[3]
References [2][4][5]

Painite is a very rare borate mineral. It was first found in Myanmar by British mineralogist and gem dealer Arthur C.D. Pain in the 1950s. When it was confirmed as a new mineral species, the mineral was named after him.[2]

The chemical makeup of painite contains calcium, zirconium, boron, aluminium and oxygen (CaZrAl9O15(BO3)). The mineral also contains trace amounts of chromium and vanadium, which are responsible for Painite's typically orange-red to brownish-red color,[1][6] similar to topaz. The crystals are naturally hexagonal in shape, and, until late 2004, only two had been cut into faceted gemstones.[7]

Discovery and occurrence

Extensive exploration in the Mogok region has identified several new painite occurrences that have been vigorously explored resulting in several thousand new painite specimens.[6]

References

  1. 1 2 T Armbruster; N Dobelin; A Peretti; D Gunther; E Reusser; B Grobety (2004). "The crystal structure of painite CaZrB(Al9O18) revisited" (PDF). American Mineralogist. 89: 610–613.
  2. 1 2 3 4 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (2003). "Paynite". Handbook of Mineralogy (PDF). V (Borates, Carbonates, Sulfates). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209740. Retrieved December 5, 2011.
  3. 1 2 3 Claringbull GF, Hey MH, Payne CJ (1957). "Painite, a New Mineral from Mogok, Burma". Mineralogical Magazine. 31 (236): 420–5. doi:10.1180/minmag.1957.031.236.11.
  4. ↑ Painite. Webmineral. Retrieved on 2012-05-28.
  5. ↑ Painite. Mindat.org. Retrieved on 2012-05-28.
  6. 1 2 Painite history at Caltech. Minerals.gps.caltech.edu. Retrieved on 2012-05-28.
  7. ↑ Ten gemstones that are rarer than diamond. io9.com

Media related to Painite at Wikimedia Commons [[Category:Hexagonal minerals]

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