Diaspore, AlO(OH), is the grayish clear bladed mineral visible on the right side of this specimen. It is sandwiched between layers of a fine grained, altered, c — Photo: Darla Sondrol · CC0
Diaspore
Also known as: Zultanite / Csarite (gem var.).
Aluminium oxide-hydroxide isostructural with goethite — a bauxite component whose gem variety (zultanite) changes color.
Intro adapted from Wikipedia (CC BY-SA).
Diaspore is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula AlO(OH).
It crystallizes in the orthorhombic crystal system (space group Pbnm). It is a member of the Diaspore structural group.
Key properties: Mohs hardness 6.5–7; specific gravity 3.2–3.5; typically white or gray or colorless or brown or pink; white streak; Adamantine, vitreous, pearly on cleavage faces luster; refractive index 1.717; optically biaxial.
IMA symbol Dsp, grandfathered status — known before the IMA’s founding, named in 1801.
Typically a final product of diagenesis in bauxite deposits formed by the tropical weathering of alumino-silicate rocks; from hydrothermal alteration of aluminous minerals; a hydrothermal mineral in some alkalic pegmatites.
It is found associated with Corundum, magnetite, margarite, chloritoid, spinel, chlorite, gibbsite, böhmite, sillimanite, lepidocrocite, hematite, kaolinite, halloysite.
Its name comes from the Greek for to scatter, in allusion to its decrepitation under the blowpipe.
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