Alunogen

Alunogen, partially outdated and synonymously known as hair salt, Keramohalit, Katharit or Katherit, Stipterit or Stypterit or sulfuric acid, alumina, is a rarely occurring mineral from the mineral class of sulfates. It crystallizes in the triclinic crystal system with the chemical composition Al 2 [ SO4 ] 3 • (12 5) H2O. It thus is a crystal of hydrous aluminum sulfate ( " hydrate "). Alunogen rarely developed transparent, tabular crystals or twins with pseudohexagonal symmetry of a few millimeters in size. He usually can be found in the form racemose, nieriger, stalaktitischer or fibrous to granular mineral aggregates and crusty coatings.

Special Features

Reiner Alunogen is colorless. However, he usually appears white through his often fibrous or granular structure and the associated multiple refraction. Various foreign admixtures can also assume a gray, yellowish or reddish color Alunogen.

Alunogen is slightly soluble in water.

Etymology and history

The mineral was named after the Latin word "alum " of alum and the Greek word " genos " for source as a reference to its use as Alaunquelle. Was first described scientifically in 1832 by François Sulpice Alunogen Beudant.

Classification

In the now outdated, 8th edition of the classification of minerals according to the Strunz Alunogen belongs to the department of " hydrous sulfates without foreign anions ."

The revision of the Strunz'schen Mineral classification in the 9th edition of this department was precisely divided by the size of the involved cations and the Alunogen can be found in the corresponding sub-department "With only medium-sized cations ".

The mostly commonly used in English-speaking classification of minerals according to Dana sorted the Alunogen also in the class of sulfates ( and related compounds ), there, however, in the department of " hydrated acids and sulfates with the general composition (A ) 2 ( XO4 ) 3 • x (H2O) "where he is the unnamed group 29.08.06 as the only member.

Education and Locations

Alunogen forms on the one hand as a weathering product in pyrite - and aluminum -containing rocks, but may on the other hand also be caused by Resublimation from volcanic gases or burning heaps. Accordingly, Alunogen usually found in paragenesis with pyrite and marcasite, but also with epsomite, gypsum, Halotrichit, melanterite and Pickeringite. Due to its high water solubility, it is sometimes ago that he swells in liquid form from coal - clefts.

Worldwide, Alunogen so far (as of 2010) are detected at around 210 localities. Known localities for crystals include Adelaide in Australia, Fries village near Bonn in Germany, Opalbanya in Hungary, Dexter No. 7 Mine Calf Mesa in Utah and at Mt Alum in New Mexico in the United States. Furthermore, Alunogen place in the form of aggregates in the Opalgruben of Dubník in Slovakia.

Crystal structure

Alunogen crystallized in the triclinic space group with lattice parameters a = 7.42 Å; b = 26.97 Å; c = 6.06 Å; α = 89.9 °; β = 97.6 ° and γ = 91.9 ° and two formula units per unit cell.