Brazilianite

Infobox mineral
name = Brazilianite
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formula = sodiumaluminum₃(phosphorus oxygen₄)₂(hydroxide)₄
sodium aluminum phosphate hydroxide
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color = Yellow, green, colorless
habit = Prismatic; Spherical druses
system = Monoclinic
twinning =
cleavage = [010] Good
fracture = Conchoidal
mohs = 5.5
luster = Vitreous
refractive = 1.60 - 1.62
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birefringence = 0.021
pleochroism =
streak = White
gravity = 2.98
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diaphaneity = Transparent to translucent
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Brazilianite, whose name derives from its country of origin, Brazil, is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites. It is a much sought after precious stone, usually ground into facet cuts, and it is a very popular item with collectors.

It occurs in the form of perfect crystals grouped in druses, in pegmatites, and is often of precious-stone quality. The only noted deposit of brazilianite is in the surroundings of Conselheiro, Pena, in the state of Minas Gerais in Brazil. During the past few years this deposit has yielded a great quantity of beautiful raw material, which has included crystals of surprisingly large dimensions and perfectly bounded crystal faces.

Some of these are found on leaves of muscovite with their strong silvery glitter, ingrown in their parent rock. Such specimens are not ground, but find their way into museums and private collections. The most exquisite crystals, dark greenish-yellow to olive-green, sometimes measure up to 12 cm in length and 8 cm in width. Crystals of similar shape and dimensions have discovered in another deposit in Minas Gerais, near Mantena, but they lack the perfection of the crystal bounding. Brazilianites have also been discovered in many large collections; they originated from the Palermo mine and the Charles Davis mine in Grafton County, New Hampshire, USA.

References

* [http://webmineral.com/data/Brazilianite.shtml WebMineral Listing]
* [http://www.mindat.org/min-760.html MinDat Listing]
* [http://mineral.galleries.com/minerals/phosphat/brazilia/brazilia.htm Mineral Galleries Listing]