Brazilianite

Brazilianite is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites. It was originally found in Brazil, and was named after the country in which it was first found.

BrazilianiteBrazilianite from type locality, Conselheiro Pena, Minas Gerais, BrazilGeneralCategoryPhosphate mineralsFormula
(repeating unit)NaAl3(PO4)2(OH)4
sodium aluminium phosphate hydroxideStrunz classification8.BK.05Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP21/nUnit cella = 11.229 Å,
b = 10.142 Å,
c = 7.098 Å; β = 97.4°; Z = 4IdentificationColorYellow, green, colorlessCrystal habitPrismatic crystals, may be radially-fibrous or globular drusesCleavage(010) Distinct to goodFractureConchoidalMohs scale hardness5.5LusterVitreousStreakWhiteDiaphaneityTransparent to translucentSpecific gravity2.98Optical propertiesBiaxial (+)Refractive indexnα = 1.602 nβ = 1.609 nγ = 1.621 - 1.623Birefringenceδ = 0.019 - 0.021References
It occurs in the form of perfect crystals grouped in druses, in pegmatites, and is often of precious-stone quality. One noted deposit of brazilianite is in the surroundings of Conselheiro Pena, in Minas Gerais, Brazil.

Some of these are found on leaves of muscovite with their strong silvery glitter, ingrown in their parent rock. The crystals, dark greenish-yellow to olive-green, sometimes measure up to 12 cm (4.7 in) in length and 8 cm (3.1 in) in width. Crystals of similar shape and dimensions have been discovered in another deposit in Minas Gerais, near Mantena, but they lack the perfection of the crystal form. Many brazilianites found in mineral collections originated from the Palermo and the Charles Davis mines in Grafton County, New Hampshire.

Category:Gemstones
Category:Geology
Category:Phosphate minerals
Category:Sodium compounds