Mejillonesite
| Mejillonesite | |
|---|---|
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| General and classification | |
| other names |
IMA 2010-068 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pbca (No. 61) |
| Lattice parameters | a = 16.295 (1) Å ; b = 13.009 (2) Å; c = 8.434 (1) Å Please complete the source as an individual reference |
| Formula units | Z = 8 Please complete the source as an individual reference |
| Frequent crystal faces | {100} |
| Physical Properties | |
| Mohs hardness | 4th |
| Density (g / cm 3 ) | measured: 2.36; calculated: 2.367 |
| Cleavage | perfect according to {100}, good according to {010} and {001} |
| Break ; Tenacity | uneven; brittle |
| colour | colorless |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.507 (2) n β = 1.531 (2) n γ = 1.531 (2) |
| Optical character | biaxial negative |
| Axis angle | 2V = 15 ° (measured); 0 ° (calculated); at 589 nm |
Mejillonesite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition NaMg 2 (PO 3 OH) (PO 4 ) (OH) ⋅H 5 O 2 , so from a chemical point of view it is a sodium - magnesium phosphate with the peculiarity that its crystal water in the form of Zundel- Cations (H 5 O 2 + ) is bound. In addition to mejillonesite, only the minerals afwillite and rhomboclase are known, which have bound their crystal water in this way.
The colorless and transparent mejillonesite develops thick tabular to prismatic crystals with shiny glass surfaces of a maximum of a few millimeters in size, which are usually arranged in radial mineral aggregates .
Etymology and history
Mejillonesite was discovered by chance in 2010 as part of an international cooperation between scientists from Brazil (Daniel Atencio, José MV Coutinho, Reynaldo R. Contreira Filho), Germany ( Thomas Witzke , Gunnar Färber), Italy (Fabrizio Nestola) and Russia (Nikita V. Chukanov, Aleksandr E. Zadov).
Thomas Witzke and Gunnar Färber analyzed various mineral samples from Chilean guano discovery sites along the coast when it was discovered that one of the samples from Cerro Mejillones did not match the pattern of known minerals from the X-ray diffractometer . After it was clearly established that the mineral sample from Mejillones was a new mineral, Witzke also determined the name according to its type locality . The full mineral description and the chosen name were submitted to the International Mineralogical Association (IMA) for review (IMA accession number : 2010-068 ) and approved in the same year.
Type material of the mineral was deposited on the one hand in the "Museu de Geociências" of the University of São Paulo in Brazil (catalog no. DR712) and on the other hand in the Fersman Mineralogical Museum of the Russian Academy of Sciences in Moscow (catalog no. 4043/1; fragment from Holotype).
classification
Mejillonesite was only recognized as an independent mineral by the IMA in 2010 and the discovery was only published in 2012. An exact group assignment in the 9th edition of Strunz's mineral system is therefore not yet known, as the system was last updated by the IMA in 2009.
However, since the mineral is a water-containing phosphate with additional anions (OH etc.) as well as with large and medium-sized cations (Na, Mg) and a molar ratio of (OH etc.): RO 4 = 2: 1, it will probably be in the subdivision Phosphates with other anions, with H 2 O, with large and medium-sized cations, (OH etc.): RO 4 = 2: 1 (system no. 8.DL. ) sorted.
Crystal structure
Mejillonesite crystallizes orthorhombically in the space group Pbca (space group no. 61) with the lattice parameters a = 16.295 (1) Å ; b = 13.009 (2) Å and c = 8.434 (1) Å and 8 formula units per unit cell .
Education and Locations
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Mejillonesite was found in the form of isolated crystal aggregates in thin zones within fine-grained opal - zeolite on the northern slope of Cerro Mejillones in Chile. Its type locality is also the only known locality for Mejillonesit where the mineral addition Opal and zeolite even with Bobierrit , gypsum , clinoptilolite -Na and K socialized occurred.
See also
literature
- Peter A. Williams, Frédéric Hatert, Marco Pasero, Stuart Mills: New Minerals approved in 2010, nomenclature modifications approved in 2010 by the Commission on new minerals, nomenclature and classification International Mineralogical Association ( PDF 277.4 kB )
- Daniel Atencio, Nikita V. Chukanov, Fabrizio Nestola, Thomas Witzke, José MV Coutinho, Aleksandr E. Zadov, Reynaldo R. Contreira Filho, Gunnar Färber: Mejillonesite, a new acid sodium, magnesium phosphate mineral, from Mejillones, Antofagasta, Chile , In: American Mineralogist , Volume 97 (2012), pp. 19-25, doi: 10.2138 / am.2012.3867 ( PDF 147.9 kB )
Web links
- Mineral Atlas: Mejillonesite (Wiki)
- DRadio Wissen - Mineralogy: Discoveries in Susanne Arlt's laboratory on May 13, 2011 ( Memento from April 29, 2013 in the web archive archive.today ) (Interview with Thomas Witzke, among other things, on the discovery of mejillonesite)
Individual evidence
- ↑ Original description, see literature
- ↑ IMA / CNMNC List of Mineral Names, Feb. 2013 - Mejillonesite (PDF; 1.4 MB)
- ↑ Original description, see literature
- ↑ DRadio Wissen - Mineralogie: Discoveries in Susanne Arlt's laboratory on May 13, 2011 ( Memento from April 29, 2013 in the web archive archive.today ) (Interview with Thomas Witzke, among other things, on the discovery of mejillonesite)
- ↑ IMA / CNMNC List of Mineral Names, 2009 (PDF; 1.9 MB)
- ↑ Mindat - Mejillonesite