Bischofite

Bishofite is a rarely occurring mineral from the mineral class of " halides ". It crystallizes in the monoclinic crystal system with the composition of MgCl2 • 6H2O, is thus seen chemically a hydrous magnesium chloride.

Bishofite rarely develops colorless crystals short prismatic habit, which are stretched along the c -axis. He usually can be found in leafy form, fibrous or granular mineral aggregates of white paint, let the light only shine through.

With a Mohs hardness 1-2 bishofite belongs to the soft minerals that are similar to the reference minerals Talk ( 1) and gypsum ( 2 ) can be scratched with a fingernail.

Special Features

Bishofite is readily soluble in water and very hygroscopic, so quickly absorbs moisture from the environment and then melts away. Therefore, the mineral should always be stored in an airtight container. Besides acting bishofite also astringent ( astringent ).

Etymology and history

Was first discovered in bishofite potash Leopold Hall at Staßfurt and described by Carl Ochsenius (1830-1906), who named the mineral matter of urgency by Karl Gustav Bischof (1792-1870) to him for his services to chemistry as one of the most important auxiliary sciences of geology to honor. At the same time, however, wanted to know Ochsenius also thought the merits of the hill council and former director of the salt works Staßfurter F. Bishop.

A first described by Fischer in 1862 as bishofite mineral turned out after further investigation than the already known mineral Plumbogummit.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the bishofite belonged to the mineral class of " halides " and then to the Department of "simple halides ," where he had a together with Antarcticite, Eriochalcit, hydrohalite, Nickelbischofit, Rokühnit and Sinjarit independent group was formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the bishofite also in the class of " halides ", there, however, in the fine already divided department of a "Simple halides with H2O" a. This department is also further subdivided by the molar ratio of the metal involved ( M) to the halogen (X), so that the mineral according to its composition in the subsection "M: X = 1: 2" to find where it is the only member of the untitled set 3.BB.15 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the bishofite in the class and of the same department of the " halides ". Here he is as the namesake of the " Bischofitgruppe " with the system no. Within the sub-division of " AX2 water outdoor and water-containing halides with the formula" to find 09:02:09 and the other Member Nickelbischofit.

Education and Locations

Bishofite formed in saline deposits, but possibly also from secondary carnallite, with which it occurs alongside associated halite and Kieserit.

A rare mineral formation could bishofite far (as of 2011) are detected only at a few localities. So far are considered to be known about 30 points. Apart from its type locality Leopoldshall the mineral still occurred in Germany in the past also in the vicinity of Staßfurter potash deposit pits " Berlepsch ", " Brefeld " ( Tarthun ) and Aschersleben in Saxony- Anhalt, and at Neuhof and the Werra Valley in Hesse; at Hänigsen, Wath and Vienenburg in Lower Saxony and in Thuringia flag on.

Other localities include the "PCS Mine" in Rocanville in the Canadian province of Saskatchewan; the Qinghai Lake, the Qarhan Salt Lake and the Salt Lake Dalangtan in China; the " Recsk Mine" in Hungarian Matra Mountains; the pits " Santa Caterina " and " Pasquasia " on Sicily in Italy; in Aksaital and Atyrau in Kazakhstan; the Dutch municipality of Veendam; Kłodawa in Poland; the volcano Tolbachik in the Russian region of Kamchatka; Krasnoperekopsk in Ukraine and Carlsbad and the Tularosa Basin, Salduro (Utah ) and Wendover in the United States.

Crystal structure

Bishofite crystallizes in the monoclinic space group C2 / m ( Raumgruppen-Nr. 12) with the lattice parameters a = 9.86 Å; b = 7.11 Å; c = 6.07 Å and 93.8 ° β = and 2 formula units per unit cell.