Diaspore: Properties and Occurrence

Diaspore also known as diasporite, empholite, kayserite, or tanatarite, is an aluminum oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. The name, which was coined by René Just Haüy, is from the Greek for διασπείρειν, to scatter, in allusion to its decrepitation on heating. Diaspore, along with gibbsite and boehmite, is a major component of the aluminum ore bauxite.

It was first described in 1801 as an occurrence in Kramatorsk Zavod, Sverdlovskaya Oblast, Middle Urals, Russia. Though Diaspore is found in several localities throughout the world, the only source of gemstone material is in a Bauxite deposit in the Anatolian Mountains of central Turkey.

General Information

  • Category: Oxide mineral
  • Formula: α-AlO(OH)
  • Crystal system: Orthorhombic
  • Crystal class: Dipyramidal (mmm)

Properties

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 luster is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. The specific gravity is 3.4. When heated before the blowpipe it decrepitates violently, breaking up into white pearly scales.

  • Color: White, pale gray, colorless, greenish gray, brown, pale yellow, pink, purple; may exhibit color change
  • Crystal habit: Platey, elongated to acicular crystals; also stalactitic, foliated, scaly, disseminated and massive
  • Fracture: Conchoidal
  • Tenacity: Very brittle
  • Mohs scale hardness: 6.5 – 7
  • Luster: Adamantine, vitreous, pearly on cleavage faces
  • Diaphaneity: Transparent to translucent
  • Specific gravity: 3.1 – 3.4
  • Optical properties: Biaxial (+)
  • Solubility: Insoluble

Occurrence

The mineral occurs as an alteration product of corundum or emery and is found in granular limestone and other crystalline rocks. Well-developed crystals are found in the emery deposits of the Urals and at Chester, Massachusetts, and in kaolin at Schemnitz in Hungary. If obtainable in large quantity, it would be of economic importance as a source of aluminum.

Csarite, ottomanite, and zultanite are trade names for gem-quality diaspore (also known as Turkish diaspore) from the İlbir Mountains of southwest Turkey.

 

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