Erikapohlit
| Erikapohlit | |
|---|---|
| General and classification | |
| other names |
IMA 2010-090 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
| Similar minerals | Keyit |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 12.6564 Å ; b = 12.7282 Å; c = 6.9148 Å β = 113.939 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | not measurable |
| Density (g / cm 3 ) | 4.55 (calculated) |
| Cleavage | not specified; not specified |
| Break ; Tenacity | not specified |
| colour | deep blue |
| Line color | pale blue |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive index | n = 1.78 (calculated) |
| Optical character | biaxial |
Erikapohlite is a very rarely occurring mineral from the mineral class of phosphates , arsenates and vanadates . It crystallizes in the monoclinic crystal system with the chemical composition Cu 3 (Zn, Cu, Mg) 4 Ca 2 [AsO 4 ] 6 ∙ 2H 2 O and is thus chemically a water-containing copper - zinc - calcium - arsenate .
Erikapohlit develops up to 0.7 mm wide, deep blue colored seams from very thin lamellar aggregates within masses of granular quartz.
Etymology and history
The type grade of Erikapohlite was bought by the mineral collector Georg Gebhard in 1994 together with other minerals in the Tsumeb mine. The material, which is very conspicuous due to its color, has been known as the unknown Ca-Cu-Zn-As mineral ("GS 5") since 1999, according to initial investigations. The mineral was recognized by the International Mineralogical Association (IMA) in 2010 and described as Erikapohlite in 2013 by Jochen Schlüter , Thomas Malcherek , Boriana Mihailova and Georg Gebhard . It was named after the German entrepreneur and mineral collector Erika Pohl-Ströher (1919–2016), who transferred her valuable mineral collection of around 80,000 specimens to the Pohl-Ströher Mineral Foundation in 2004 , with a view to its inventory, scientific supervision and public To ensure permanent accessibility. This collection was made available on permanent loan from the TU Bergakademie Freiberg . After the renovation of Freudenstein Castle , around 3,500 exhibits have been on public display in the terra mineralia exhibition since October 20, 2008 .
Type material of the mineral (holotype) is kept in the Mineralogical Museum of the University of Hamburg in Germany (catalog no. TS117 c).
classification
Erikapohlite was only recognized as an independent mineral by the International Mineralogical Association (IMA) in 2010 and the discovery was only published in 2013. A precise group assignment in the 9th edition of Strunz's mineral classification is therefore not yet known.
Crystal structure
Erikapohlite crystallizes in the monoclinic crystal system in the space group C 2 / c (space group no. 15) with the lattice parameters a = 12.6564 Å ; b = 12.7282 Å; c = 6.9148 Å and β = 113.939 ° as well as two formula units per unit cell .
The crystal structure of Erikapohlite can possibly be derived from that of the related structures of the minerals Keyite and Nickenichite . To clarify the assignment, however, it is necessary to determine the real symmetry of Erikapohlit. Whether C 2 / c is actually the space group in which the mineral crystallizes can only be determined using single crystal data or better resolved powder data.
Chemism
Erikapohlit has the measured composition Cu 3 (Zn 2.48 Cu 0.93 Mg 0.77 Fe 0.01 ) Σ4.19 Ca 2.04 As 6.20 O 24.71 ∙ 1.29H 2 O. This formula can can be written simply as Cu 3 (Zn, Cu, Mg) 4 Ca 2 (AsO 4 ) 6 ∙ 2H 2 O. SEM-EDX backscattered electron images from Erikapohlit show chemical inhomogeneities in this mineral, which can be explained by varying levels of magnesium , zinc and copper . Further analysis also showed that there are zones in the zinc-dominated Erikapohlite with Mg and even Cu dominance.
properties
morphology
Erikapohlit forms seams up to 0.7 mm wide from very thin aggregates consisting of lamellar microcrystals within masses of granular quartz.
physical and chemical properties
The aggregates of Erikapohlite are deep blue, the line color of the mineral is described as light blue. The surfaces of the transparent crystals have a glass-like sheen . Due to the small crystal size, the Mohs hardness of Erikapohlite cannot be determined. The calculated density of the mineral is 4.55 g / cm³.
Modifications and varieties
Erikapohlite is the natural calcium-dominant analogue of the cadmium-dominated keyite, Cu 2+ 3 Zn 4 Cd 2 [AsO 4 ] 6 · 2H 2 O. Analyzes mentioned in the type publication showed that there are zones with Mg and even in zinc-dominated Erikapohlite Cu dominance there. This means that there are two further potential minerals, which will then be a water-containing copper - magnesium - calcium - arsenate and a water-containing copper-copper-calcium arsenate.
Education and Locations
Erikapohlit comes from the second (lower) oxidation zone of the seated in dolomite stones hydrothermal ore deposit polymetallic Tsumeb and was here at the 44th sole recovered. It is a typical secondary mineral that was formed here from the alteration of tennantite . Erikapohlit is closely related Lammerit , Konichalcit granular quartz and an unknown, and brownish transparent, amorphous Zn-Fe-Cu- (Mg-Ca) arsenate associated .
So far (as of 2016) the mineral could only be found at its type locality . The type locality is the world-famous Cu-Pb-Zn-Ag-Ge-Cd deposit of the "Tsumeb Mine" (Tsumcorp Mine) in Tsumeb , Oshikoto region , Namibia .
See also
literature
- Jochen Schlüter, Thomas Malcherek, Boriana Mihailova, Georg Gebhard (2016): The new mineral erikapohlite, Cu 3 (Zn, Cu, Mg) 4 Ca 2 (AsO 4 ) 6 ∙ 2H 2 O, the Ca-dominant analogue of keyite, from Tsumeb, Namibia. In: New Yearbook Mineralogie Abhandlungen Volume 190 (Issue 3), pp. 319–325.
Web links
Individual evidence
- ↑ a b c d e f g h i j k l m n o Jochen Schlüter, Thomas Malcherek, Boriana Mihailova, Georg Gebhard (2016): The new mineral erikapohlite, Cu 3 (Zn, Cu, Mg) 4 Ca 2 (AsO 4 ) 6 ∙ 2H 2 O, the Ca-dominant analogue of keyite, from Tsumeb, Namibia. In: New Yearbook Mineralogie Abhandlungen , Volume 190 (Issue 3), pp. 319–325.
- ↑ Georg Gebhard: Tsumeb . 1st edition. GG Publishing, Grossenseifen 1999, p. 320 .
- ↑ Mindat - Number of localities for Erikapohlit
- ↑ Find location list for Erikapohlit in the Mineralienatlas and Mindat