Scorpionite
| Scorpionite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2005-010 |
| chemical formula | Ca 3 Zn 2 [(OH) 2 | (PO 4 ) 2 | (CO) 3 ] · H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DO.45 43.05.24.01 |
| Similar minerals | Scholzite (if in sword-shaped crystals) |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 19.045 Å ; b = 9.320 Å; c = 6.525 Å β = 92.73 ° |
| Formula units | Z = 4 |
| Frequent crystal faces | {100}, {110}, {111}, {221}, {131}, { 1 01} |
| Twinning | no |
| Physical Properties | |
| Mohs hardness | 3.5 |
| Density (g / cm 3 ) | 3.15 (measured); 3.17 (calculated) |
| Cleavage | is missing |
| Break ; Tenacity | uneven; brittle |
| colour | colorless |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.5884 n β = 1.6445 n γ = 1.6455 |
| Birefringence | δ = 0.0571 |
| Optical character | biaxial negative |
| Axis angle | 2V = 15.0 |
| Other properties | |
| Chemical behavior | easy dissolution in dilute HCl with bubbling evolution of CO 2 |
| Special features | yellow fluorescence |
Scorpionite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates " with the chemical formula Ca 3 Zn 2 [(OH) 2 | (PO 4 ) 2 | (CO) 3 ] · H 2 O. Scorpionite is chemically speaking, this is a water-containing calcium - zinc - phosphate - carbonate with additional hydroxide ions .
Scorpionite crystallizes in the monoclinic crystal system and only develops needle-like crystals stretched along the c-axis, up to 0.5 mm long and up to 40 μm wide.
Etymology and history
Scorpionite was found during the screening of material which was collected in October 2003 by Ludger Krahn together with Gregor Borg and Karen Kärner in the Skorpion Mine. Colorless, needle-like crystals could not be identified with X-ray diffraction methods and turned out to be a new mineral. In 2008, a research team with Werner Krause, Herta Effenberger, Heinz-Jürgen Bernhardt and Olaf Medenbach described them as a scorpionite.
The mineral was recognized by the International Mineralogical Association (IMA) in 2005 and named after its type locality , the Skorpion zinc deposit near Rosh Pinah , Oranjemund in the ǁKaras region , Namibia .
Type material of the mineral (holotype) is kept in the Institute for Mineralogy, Geology and Geophysics of the Ruhr University Bochum in Germany (catalog no. IMA 2005-010).
classification
Since the scorpionite was only recognized as an independent mineral in 2005, it is not listed in the Strunz mineral system (8th edition), which has been outdated since 2001 .
The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), classifies the scorpionite in the category of “phosphates etc. with additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the other anions to the phosphate, arsenate or vanadate complex, so that the mineral according to its composition in the subsection "With CO 3 , SO 4 , SiO 4 " is found where it is the only member of the unnamed group 8.DO.45 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the scorpionite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is to be found as the sole member of the unnamed group 43.05.24 within the subdivision Compound Phosphates etc., ( Compound anions containing water with hydroxyl or halogen) .
Crystal structure
Scorpionite crystallizes in the monoclinic crystal system in the space group C 2 / c (space group no. 15) with the lattice parameters a = 19.045 Å ; b = 9.320 Å; c = 6.525 Å and β = 92.73 °; as well as four formula units per unit cell .
The crystal structure of Skorpionits consists of corrugated layers to be connected, corner-sharing ZnO 4 - and PO 4 - tetrahedra . The structure forms a three-dimensional network of [Ca2 2 Zn 2 (OH) 2 (PO 4 ) 2 ] 0 and [Ca1 (CO 3 ) (H 2 O)] 0 layers, which are formed by hydrogen bonds and Ca-O Ties are connected.
properties
morphology
According to [001], scorpionite forms needle-like to latte, according to (100) tabular crystals up to 0.5 mm in length and up to 40 μm in width, which are typically confused with one another. The supporting shapes of the crystals are the pinacoid {100} and the prism {110}, furthermore the shapes {111}, {221}, {131}, { 1 01}, which form the head surfaces , were identified on the crystals .
physical and chemical properties
The crystals of the scorpionite are colorless to white, the line color of the mineral is also described as white. The surfaces of the scorpionite crystals have a glass-like sheen . Although the scorpionite should not fluoresce in long or short-wave UV light , some levels show an intense yellow fluorescence in short-wave UV light.
Due to its brittleness, the mineral breaks in a similar way to glass or quartz , with the edges of the break being uneven. With a Mohs hardness of 3.5, scorpionite is one of the medium-hard minerals that, like the reference mineral fluorite, can be easily scratched with a pocket knife. The calculated density of the mineral is 3.17 g / cm 3 . There is no cleavage .
Scorpionite dissolves easily in dilute hydrochloric acid , producing CO 2 , which escapes in a bubbling manner.
Education and Locations
Scorpionite is found as a secondary mineral on an oxidized zinc deposit that has formed through the weathering of sediments and volcanic rocks, in which sulfide minerals were finely distributed. The adjacent rock is heavily folded, broken and metamorphic (lower amphibolite facies) overprinted. The main ore minerals in this deposit are hemimorphite , smithsonite , sauconite and hydrozincite . These minerals occur as fillings in intergranular cavities, fractures and breccias as well as displacements of feldspars and mica mainly in arkose-like metarenites, to a lesser extent in volcanoclastic metasediments. Scorpionite is associated with tarbuttite , hydrozincite and gypsum .
So far (as of 2016) the mineral could only be found at its type locality, the zinc deposit Skorpion near Rosh Pinah , Oranjemund in the region of ǁKaras , Namibia .
use
Scorpionite with end link composition consists of about 29% zinc and is therefore a rich zinc ore that has certainly already been mined and smelted in the Skorpion mine. However, due to its rarity, the mineral is much more attractive to collectors.
See also
literature
- Werner Krause, Herta Effenberger, Heinz-Jürgen Bernhardt and Olaf Medenbach (2008): Skorpionite, Ca 3 Zn 2 (PO 4 ) 2 CO 3 (OH) 2 H 2 O, a new mineral from Namibia: description and crystal structure In : European Journal of Mineralogy , Volume 20, 271-280 ( PDF, 1.98 MB ).
Web links
- Mineral Atlas: Scorpionite (Wiki)
- Mindat - Scorpionites
- Webmineral - Scorpionites
- RRUFF Database-of-Raman-spectroscopy - Scorpionites
- American-Mineralogist-Crystal-Structure-Database - Scorpionites
Individual evidence
- ↑ a b c d e f g h i j k Werner Krause, Herta Effenberger, Heinz-Jürgen Bernhardt and Olaf Medenbach (2008): Skorpionite, Ca 3 Zn 2 (PO 4 ) 2 CO 3 (OH) 2 · H 2 O , a new mineral from Namibia: description and crystal structure In: European Journal of Mineralogy , Volume 20, 271-280 ( PDF, 1.98 MB ).
- ↑ Skorpionite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 130 kB ).
- ↑ Mindat - Number of localities for Scorpionite