Wit
| Wit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2011-084 |
| chemical formula | Na 4 K 4 Ca (NO 3 ) 2 (SO 4 ) 4 · 2H 2 O |
|
Mineral class (and possibly department) |
Sulphates (selenates, tellurates, chromates, molybdates and tungstates) |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 24.902 (2) Å ; b = 5.3323 (4) Å; c = 17.246 (1) Å β = 94.281 (7) ° Please complete the source as an individual reference |
| Formula units | Z = 4 Please complete the source as an individual reference |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 2.40 (2); calculated: 2.403 |
| Cleavage | clearly after {001} |
| Break ; Tenacity | uneven |
| colour | colorless to white |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.470 (5) n β = 1.495 (5) n γ = 1.510 (5) |
| Optical character | biaxial negative |
| Axis angle | 2V = 50 to 70 ° |
Witzigkeit is a very rarely occurring mineral from the mineral class of " sulfates (selenates, tellurates, chromates, molybdates and tungstates)". It crystallizes in the monoclinic crystal system with the composition Na 4 K 4 Ca (NO 3 ) 2 (SO 4 ) 4 · 2H 2 O, so chemically speaking it is a water-containing sodium - potassium - calcium - nitrate sulfate. After Darapskit , Ungemachit and Humberstonit , Witzkeit is only the fourth known nitrate sulfate.
Wit is colorless and transparent and has so far only been found in the form of tiny, tabular crystals up to about 140 micrometers in length. These show clear cleavage at right angles to the c-axis and a glass-like gloss on the surfaces.
Etymology and history
Witzkeit was first discovered in the guano mining area at Punta de Lobos in the Chilean region of Tarapacá . It was described in 2011 by Fabrizio Nestola, Fernando Cámara, Nikita V. Chukanov, Daniel Atencio, José MV Coutinho, Reynaldo R. Contreira Filho and Gunnar Färber, who named the mineral after the German mineralogist Thomas Witzke (* 1963), for his contributions to honor mineral transformation or weathering processes and their products, which also led to the first description of numerous new, mainly secondary minerals.
The type material of the mineral is kept in the Mineralogical Collection of the Geoscientific Department of the University of Padua in Italy (Catalog No. MMP M10009).
classification
Witzkeit was only recognized as an independent mineral by the International Mineralogical Association (IMA) in 2011 and the discovery was not published until 2012. A precise group assignment in the 9th edition of Strunz's mineral classification is therefore not yet known. Since the mineral is, however, a close relative of darapskite , ungemachite and humberstonite , which, due to its composition , belongs to the mineral class of "sulfates (selenates, tellurates, chromates, molybdates and tungstates)" and there in the subdivision of hydrous sulfates with other anions and large up to medium-sized cations as well as NO 3 , CO 3 , B (OH) 4 , SiO 4 or IO 3 can be found, Witzkeit will probably also be sorted there.
Crystal structure
Witzkeit crystallizes monoclinically in the space group space group C 2 / c (space group no. 15) with the lattice parameters a = 24.902 (2) Å ; b = 5.3323 (4) Å; c = 17.246 (1) Å and β = 94.281 (7) ° and 4 formula units per unit cell .
properties
Witzigkeit is water-soluble, although it dissolves slowly in cold water and a little faster in water at around 50 ° C.
Education and Locations
Wit was formed, associated with dittmarite and nitronatrite , in the oxidation zone of the guano mining area on the southeast slope of Punta de Lobos in Chile, known as the type locality . It is also the only known location of the mineral to date.
See also
literature
- Fabrizio Nestola, Fernando Cámara, Nikita V. Chukanov, Daniel Atencio, José MV Coutinho, Reynaldo R. Contreira Filho, Gunnar Färber: Witzkeite: A new rare nitrate-sulphate mineral from a guano deposit at Punta de Lobos, Chile , in: American Mineralogist , Volume 97 (2012), pp. 1783–1787 doi : 10.2138 / am.2012.4109
