Mineral Species: Diaspore and Natrolite

Chemical Formula: AlO(OH)

Chemical Name: Aluminium Hydroxide

Mineral Class: Oxide

Mineral Notes: Diaspore is isomorphous with Goethite and Manganite. It often occurs 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. Diaspore may be readily distinguished from other colourless transparent minerals with perfect cleavage and pearly luster, like Talc, Brucite, and Gypsum by its greater hardness of 6.5 - 7. The mineral occurs as an alteration product of Corundum or Emery and is found in granular limestone and other crystalline rocks. Diaspore along with Gibbsite and Boehmite are the major components of the aluminium ore Bauxite.

Description: White, massive Diaspore with embedded flattened flakes of highly crystalline Natrolite. The Diaspore has a pronounced pearly luster and an unusual gritty texture.

Location: Gronsko, Czech Republic.