diaspore

{{Infobox mineral | name = Diaspore | category = Oxide mineral | image = Diaspore-Margarite-rare-09-05b.jpg | caption = | formula = α-AlO(OH) | IMAsymbol = Dsp | molweight = | strunz = 4.FD.10 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H–M symbol: (2/m 2/m 2/m) | symmetry = Pbnm | unit cell = a = 4.4007(6) Å b = 9.4253(13) Å c = 2.8452(3) Å; Z = 4 | color = White, pale gray, colorless, greenish gray, brown, pale yellow, pink, purple; may exhibit color change | habit = Platy, elongated to acicular crystals; also stalactitic, foliated, scaly, disseminated, and massive | twinning = Forms heart shaped twins on {021} or pseudohexagonal aggregates | cleavage = {010} perfect, {110} distinct, {100} in traces | fracture = Conchoidal | tenacity = Very brittle | mohs = 6.5–7.0 | luster = Adamantine, vitreous, pearly on cleavage faces | streak = | diaphaneity = Transparent to translucent | gravity = 3.1–3.4 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 1.682–1.706 nβ = 1.705–1.725 nγ = 1.730–1.752 | birefringence = δ = 0.048 | pleochroism = Strong | 2V = Measured: 84–86°Calculated: 80–84° | dispersion = r < v, weak | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = Infusible | diagnostic = | solubility = Insoluble | other = Decrepitates releasing water in closed tube on heating | alteration = | references = }}

Diaspore ()also called diasporite, empholite, kayserite, or tanatariteis an aluminium hydroxide oxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster (e.g. mica, talc, brucite, and gypsum) by its greater hardness of 6.5–7. Its specific gravity is 3.4. When heated before the blowpipe, it decrepitates violently, breaking up into white pearly scales.