Painite

Painite is a very rare borate mineral. It was first found in Myanmar by British mineralogist and gem dealer Arthur C.D. Pain who misidentified it as ruby, until it was discovered as a new gemstone in the 1950s. When it was confirmed as a new mineral species, the mineral was named after him.[2] Due to its rarity, painite can cost in the range of between US$50,000 to $60,000 per carat.

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	red
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]
Melting point	2094
Solubility	Insoluble in acids[3]
References	[2][4][5]

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 mineral's rarity is due to the fact that zirconium and boron rarely interact with each other in nature. 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 area surrounding Mogok, which comprises a large part of the extremely small region the mineral is known to exist in, has identified several new painite occurrences that have been vigorously explored resulting in several thousand new available painite specimens.[6]

• 
  Striated, euhedral painite crystal (size: 0.9×0.8×0.7 cm)
• 
  Corundum var. ruby on a large painite crystal, Mogok, Burma. (size: 3.7×3.1×2.3 cm)

References

1. 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. Archived from the original (PDF) on 2016-03-04. Retrieved 2012-05-28.
2. 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. 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. Painite history at Caltech. Minerals.gps.caltech.edu. Retrieved on 2012-05-28.
7. Ten gemstones that are rarer than diamond. io9.com

External links

• Media related to Painite at Wikimedia Commons