brushite

{{Infobox mineral | image = Brushite, Montmorillonite-445846.jpg | caption = Brushite (white) on montmorillonite | name = Brushite | category = Phosphate mineral | formula = | IMAsymbol=Bsh | strunz = 8.CJ.50 | system = Monoclinic | symmetry = Ia (no. 9) | unit cell = a = 6.265 Å, b = 15.19 Å, c = 5.814 Å; β = 116.47°; Z = 4 | color = Colorless to pale or ivory-yellow | habit = Prismatic to tabular acicular crystals; typically powdery or earthy | twinning = | cleavage = Perfect on {010} and {001} | fracture = | tenacity = Brittle | mohs = 2.5 | luster = Vitreous, pearly on cleavages | streak = | diaphaneity = Transparent to translucent | gravity = 2.328 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 1.539 – 1.540 nβ = 1.544 – 1.546 nγ = 1.551 – 1.552 | birefringence = δ = 0.012 | pleochroism = | 2V = Measured: 59 to 87° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = Readily in HCl | impurities = | alteration = | other = Piezoelectric | prop1 = | prop1text = | references = }} Brushite is a phosphate mineral with the chemical formula . Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless. It is the phosphate analogue of the arsenate pharmacolite.

==Discovery and occurrence== Brushite was first described in 1865 as an occurrence on Aves Island, Nueva Esparta, Venezuela, and named for the American mineralogist George Jarvis Brush (1831–1912). It is believed to be a precursor of apatite and is found in guano-rich caves, formed by the interaction of guano with calcite and clay at a low pH. It occurs in phosphorite deposits and forms encrustations on old bones. It may result from the runoff of fields which have received heavy fertilizer applications. Associated minerals include taranakite, ardealite, hydroxylapatite, variscite and gypsum.