Weddellite

Weddellite
	white Weddellite crust from the Cerchiara mine near Borghetto di Vara , Liguria, Italy
General and classification
other names	Calcium oxalate dihydrate
chemical formula	Ca (C 2 O 4 ) • 2 H 2 O
Mineral class; (and possibly department)	Organic compounds
System no. to Strunz ; and to Dana	10.AB.40 ( 8th edition : IX / A.01) ; 50.01.02.01
Crystallographic Data
Crystal system	tetragonal
Crystal class ; symbol	tetragonal-dipyramidal; 4 / m
Room group (no.)	I 4 / m (No. 87)
Lattice parameters	a = 12.371 Å ; c = 7.357 Å
Formula units	Z = 8
Physical Properties
Mohs hardness	4th
Density (g / cm 3 )	1.94 (measured); 1.962 (calculated)
Cleavage	well along {010}
colour	colorless, brown to yellow due to organic inclusions
Line color	White
transparency	transparent
shine	Please complete

Weddellite , 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 (C ₂ O ₄ ) · 2 H ₂ O. It forms individual colorless crystals up to four centimeters in size , which can be colored yellow or brown due to organic inclusions.

Etymology and history

Weddellite was first found during the Scottish National Antarctic Expedition (1902-1904) and described by Arthur Earland , a British oceanographer. The exact analysis of the mineral and its classification were only carried out in 1936 by FA Bannister and MH Hey. They named the mineral after the place where it was found, the Weddell Sea in Antarctica .

classification

In the Strunz system, Weddellite 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 In the outdated eighth edition it forms with Caoxit , Coskrenit- (Ce) , Glushinskit , Humboldtin , Levinsonit- (Y) , Lindbergite , Minguzzit , Moolooit , Natroxalat ,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 , Stepanovite , Wheatleyite , Whewellit , Zhemchuzhnikovite ( , Zugshunstit- Ce) the oxalate group, a subgroup of the salts of organic acids. In the new ninth edition , it forms a separate subgroup of the oxalates .

In the Dana system , Weddellite and Caoxit form a subgroup of the salts of organic acids (oxalates).

Crystal structure

Weddellite crystallizes in the tetragonal crystal system in the space group I 4 / m (space group no. 87) with the lattice parameters a = 12.371 Å and c = 7.357 Å as well as eight formula units per unit cell .

properties

Weddellite is insoluble in water; in the air it easily releases crystal water and then forms whewellite .

Education and Locations

Scanning electron microscope (SEM) image of tetragonal crystals of calcium oxalate dihydrate (Weddellite) on the surface of a kidney stone (acceleration voltage 30 kV). The long side of the figure is 0.35 mm.

Weddellite is formed authigenically in sediments through the reaction of calcite with oxalic acid , which was formed from lichen and from bat guano . In addition to the type locality , the mineral is found in several locations in Western Australia , the Gcwihaba cave near Maun in Botswana , the Vitoscha Mountains in Bulgaria , Ellesmere Island and Haliburton County in Canada , Xilin Hot in China , the Black Forest ( Germany ), Ashover in England , as well as several locations in Italy , Russia and the United States .

Weddellite can be a component of urinary stones . The storage of other urine components creates stable Weddellite crystals that can aggregate to form larger stones. Weddellite stones are mainly found in dogs and cats.

literature

Weddellit in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( PDF 63.8 kB ).

Web links

Commons : Weddellite - collection of pictures, videos and audio files

Individual evidence

^ ^A ^b Vittorio Tazzoli, Chiara Domeneghetti: The crystal structures of whewellite and weddellite: re-examination and comparison. In: American Mineralogist. 1980, 65, pp. 327-334 ( PDF ).
^ FA Bannister, MH Hey: Report on some crystalline components of the Weddell Sea. In: Discovery Reports. 1936, 13, p. 60 ( pdf ).
^ Dana Salts of Organic Acids Classification at webmineral.com. .
^ Vittorio Tazzoli, Chiara Domeneghetti: The crystal structures of whewellite and weddellite: re-examination and comparison. In: American Mineralogist. 1980, 65, pp. 327-334 ( PDF ).
↑ A. Hesse: Urolithiasis in rabbits. The origin of the names. Animal Stone Letter 7: 1/2013.

[Tazzoli-1] A ^b Vittorio Tazzoli, Chiara Domeneghetti: The crystal structures of whewellite and weddellite: re-examination and comparison. In: American Mineralogist. 1980, 65, pp. 327-334 ( PDF ).

[2] FA Bannister, MH Hey: Report on some crystalline components of the Weddell Sea. In: Discovery Reports. 1936, 13, p. 60 ( pdf ).

[3] Dana Salts of Organic Acids Classification at webmineral.com. .

[4] Vittorio Tazzoli, Chiara Domeneghetti: The crystal structures of whewellite and weddellite: re-examination and comparison. In: American Mineralogist. 1980, 65, pp. 327-334 ( PDF ).

[5] A. Hesse: Urolithiasis in rabbits. The origin of the names. Animal Stone Letter 7: 1/2013.