Weddellite
- Calcium oxalate dihydrate
Weddellit, chemically calcium oxalate dihydrate, is a very rare mineral from the mineral class of organic compounds. It crystallizes in the tetragonal crystal system with the chemical composition Ca ( C2O4 ) 2 · 2 H2O. It forms individual, up to four centimeters of colorless crystals, which can be colored yellow or brown by organic inclusions.
Special Features
Weddellit is insoluble in water, in the air, it is easy crystal water and then forms Whewellite.
Etymology and history
Weddellit was first found in the course of the Scottish National Antarctic Expedition (1902-1904) and described by Arthur Earland, a British oceanographer. The exact analysis of the mineral and its classification was not until 1936 performed by FA Bannister and MH Hey. They named the mineral after the collecting site, the Weddell Sea in Antarctica.
Classification
In the classification by Strunz Weddellit is counted among the organic compounds. In the outdated eighth edition it forms with Caoxit, Coskrenit - (Ce), Glushinskit, Humboldtin, Levinsonit - (Y), Lindbergite, Minguzzit, Moolooit, Natroxalat, Novgorodovait, Oxammit, Stepanovit, Wheatleyit, Whewellite, Zhemchuzhnikovit, Zugshunstit ( ce ) the oxalate group, a sub-group of the salts of organic acids. In the new Ninth Edition, it forms a separate subgroup of oxalates.
In the classification by Dana Weddellit forms with Caoxit a subset of the salts of organic acids ( oxalates ).
Education and Locations
Weddellit forms authigen in sediments by reaction of calcite with oxalic acid, which was formed by lichens and from bat guano. In addition to the type locality is found, the mineral among others in several localities in Western Australia, the Gcwihaba Cave near Maun in Botswana, the Vitosha Mountain in Bulgaria, Ellesmere Iceland and Haliburton County in Canada, Xilin Hot in China, the Black Forest ( Germany ), Ashover in England, as well as several places in Italy, Russia and the United States.
Weddellit may be a component of urinary stones. By incorporation of other urine constituents produces stable Weddellit crystals, which can assemble into larger stones. Weddellit Stones mainly occur in dogs and cats.
Crystal structure
Weddellit crystallizes in the tetragonal crystal system in the space group I4 / m ( Raumgruppen-Nr. 87) with the lattice parameters a = 12.371 Å and c = 7.357 Å, and eight formula units per unit cell.