Diaspore

Diaspore (also Diasporit ) is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition of AlO ( OH) and usually develops flaky, granular or massive aggregates, but also small, finely striated crystals to about 12 cm in size wide columns with predominantly developed longitudinal surface.

Reiner diaspore is colorless. However, it can by foreign admixtures white to gray, yellow, pink, green, be reddish to violet or brownish. Its Mohs hardness of 6.5 to 7, and its density is 3.3 to 3.5 g / cm ³.

Diaspore is sometimes confused because of the similarity in name with the Bleisilberantimonit Diaphorit.

Special Features

Diaspore shows distinct pleochroism, which means it appears colorless in the direction of x - axis, colorless or pale red in the direction of y -axis and pale blue or pale red in the direction of z -axis.

Chemically, diaspore significantly from aluminum hydroxide Al2O2 (OH ) 2 or AlO ( OH), with 85.02 % clay and 14.98 % water and admixtures of some iron oxide. He is blue with cobalt solution, acids do not solve it, and only after strong ignition it is soluble in sulfuric acid.

Etymology and history

The name is derived from the Greek word diaspore διασπείρειν ( diaspeirein ) for scatter. René -Just wanted to point Haiiy with the label in 1801 elected to its mineral description on its ability to atomize into small particles when heated before the blowpipe with water delivery or to burst. This property is also referred to as decrepitate ( Decrepitieren ).

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the diaspore belonged to the mineral class of " oxides and hydroxides " and then to the Department of " hydroxides and oxide hydrates ," where he, along with akaganeite, boehmite, Feitknechtit, Feroxyhyt goethite, Groutit, lepidocrocite, manganite, schwertmannite and Tsumgallit the unnamed group IV/F.6 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the diaspore in the class of " oxides and hydroxides " and then in the Department of the " Hydroxide (without V or U) " a. This division, however, is further subdivided according to the possible presence of water of crystallization as well as the crystal structure, so that the mineral according to its composition in the subsection " hydroxides with OH, without H2O; can be found with chains of edge -sharing octahedra ", where it forms the unnamed group 4.FD.10 together with Bracewellit, goethite, Groutit, Guyanait, montroseite and Tsumgallit.

The classification of minerals according to Dana assigns the diaspore in the class of " oxides and hydroxides " and there in the department of " hydroxides and hydroxy- oxides " one. Here's the diaspore eponymous and with the other members Groutit, montroseite, Bracewellit and Tsumgallit in the " Diasporgruppe ( Orthorhombic, Pnma or Pnmd ) " with the system no. 06:01:01 within the sub-division of: to find " hydroxides and hydroxy- oxides having the formula X3 O OH ".

Modifications and varieties

The connection AlO ( OH) is dimorphic, ie, occurs in nature in addition to the orthorhombic crystallized diaspore even as also orthorhombic, but crystallizing in a different space group boehmite ago.

Education and Locations

Dispor forms either hydrothermal or metamorphic from aluminum-rich minerals or in aluminum-rich rocks. Accompanying minerals include pyrophyllite and corundum. Diaspore is also a mixture proportion of bauxite.

Locations include Naxos and Ephesus ( emery ) in Greece, Schemnitz in Hungary, Kossobrodskaja the Urals, Campolungo at Faido ( in dolomite, corundum) in Switzerland, Greiner in Tyrol ( with kyanite ), Menderess in Turkey, Unionville, Chester / Massachusetts and Pennsylvania in the United States.

Crystal structure

Diaspore crystallizes in the orthorhombic crystal system, space group Pbnm, the lattice parameters a = 4.40 Å, b = 9.43 Å and c = 2.85 Å and four formula units per unit cell.

Oxygen and hydroxide ions form a hexagonal closest packing of spheres with holes on the octahedral sites, which are filled in by the aluminum. In the c- axis arise in this way long double chains of octahedra AlO6, which are held together by hydrogen bonds.

Use

Diaspore is used as abrasives and polishing agents use.