Admontite

• IMA 1978-012

Admontit is a very rarely occurring mineral from the mineral class of " borates ". It crystallizes in the monoclinic crystal system with the chemical composition Mg [ B6O7 (OH ) 6] · 4H2O, that is a hydrous magnesium borate.

Admontit forms colorless and transparent crystals to about a millimeter in size, which are only weakly developed or corroded and stretched along the c -axis. The crystal faces have a glass-like shine. With a Mohs hardness 2-3 Admontit belongs to the soft minerals that are similar to how the reference minerals gypsum ( 2) and calcite (3) either still be scratched with a fingernail or with a copper coin.

Special Features

In the water Admontit decomposes slowly.

Etymology and history

Was first discovered Admontit to the shield wall at Admont in Styria in Austria and described in 1979 by Kurt Walenta, who named the mineral after its type locality.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Admontit still belonged to the common mineral class of " carbonates, nitrates and borates " and then to the Department of " group borates ," where he along with Aksait, Mcallisterit and Rivadavit the unnamed V/H.17 group was formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Admontit into the now separate class of " borates " and there in the department of " Hexaborate ". This division, however, is further subdivided according to the crystal structure of the borate complex, so that the mineral according to its construction in the subsection " island ( Neso ) Hexaborate " is to find where it forms the unnamed group 6.FA.15 the only member.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Admontit as the outdated Strunz'sche systematics in the class of " carbonates, nitrates and borates ", there, however, in the more finely divided department of " water -containing borates with hydroxyl or halogen" a. Here he can be found as the only member of the unnamed group 26.06.03 within the sub-division of " water -containing borates with hydroxyl or halogen".

Education and Locations

Admontit forms in gypsum deposits and can be found there in accordance with this in paragenesis. Other accompanying minerals include anhydrite, Eugsterit, hexahydrite, Löweit, pyrite and quartz.

So far (as of 2011), the mineral could be detected only at its type locality shield wall at Admont in Austria.

Crystal structure

Admontit crystallizes in the monoclinic space group P21 / c ( Raumgruppen-Nr. 14) with the lattice parameters a = 12.66 Å; b = 10.09 Å; c = 11.32 Å and β = 109.6 °, and four formula units per unit cell.