Guanacoite
| Guanacoite | |
|---|---|
 Size 2.3 cm × 2.1 cm × 1.6 cm |
|
| General and classification | |
| other names |
IMA 2003-021 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.DD.10 42.04.01.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 5.459 (2) Å ; b = 16.808 (9) Å; c = 6.917 (3) Å β = 100.44 (1) ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3 |
| Density (g / cm 3 ) | measured: 3.31; calculated: 3.36 |
| Cleavage | clearly to well parallel {010} |
| Break ; Tenacity | uneven to shell-like; brittle |
| colour | blue to light blue, turquoise blue |
| Line color | white to light blue |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.664 (1) n β = 1.691 (1) n γ = 1.695 (1) |
| Birefringence | δ = 0.031 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 31 °; calculated: 42 ° |
| Other properties | |
| Chemical behavior | soluble in cold and warm acids |
Guanacoite is a very rare mineral from the mineral class of "phosphates, arsenates and vanadates" with the idealized chemical composition Cu 2 Mg 3 (OH) 4 (AsO 4 ) 2 · 4H 2 O or in the crystal chemical formula notation according to Stunz Cu 2 ( mg, Cu) mg 2 [(OH) 2 | AsO 4 ] 2 · 4H 2 O. Guanacoit is so chemically seen a hydrous copper - magnesium - arsenate with additional hydroxide .
Guanacoite crystallizes in the monoclinic crystal system , but develops only small, needle-like to prismatic crystals of about 0.7 mm in length and from light blue to turquoise blue in color.
Etymology and history
Guanacoite was first discovered in the "El Guanaco Mine" near Guanaco in the Chilean Región de Antofagasta and scientifically described by Thomas Witzke , Uwe Kolitsch , Werner Krause, Annemarie Wiechowski, Olaf Medenbach , Anthony R. Kampf, Ian M. Steele and Georges Favreau who named the mineral after its type locality .
Guanacoite was recognized as an independent mineral by the International Mineralogical Association (IMA) in 2003 under the provisional designation IMA 2003-021 . The test results and the recognized name Guanacoite were published in 2006 in the European Journal of Mineralogy 18 .
Type material , i.e. mineral samples from its type locality Guanaco, is in the mineralogical collection of the Technical University Bergakademie Freiberg in Germany under the catalog no. 79704 kept.
Independent investigations by one of the first descriptors were able to detect guanacoite in mineral samples from the Taghouni opencast mine in the Moroccan province of Ouarzazate ( Souss-Massa-Daraâ ). The type material from this site is in the collection of the Natural Science Department of the Natural History Museum of Los Angeles County under catalog no. 55435 , 55436 and 55437 .
classification
Since the guanacoite was only discovered in 2003, it is not listed in the Strunz mineral system (8th edition), which has been outdated since 2001 . Only in the "Lapis Mineralienverzeichnis", which was last published in 2014, which is still based on the classic system of Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system no. VII / D.16-25 . In the "Lapis Classification", this corresponds to the class of "phosphates, arsenates and vanadates" and then the department "water containing phosphates, with foreign anions " where Guanacoit with Akrochordit , Chenevixit and Luetheit forms an independent but unnamed group.
The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns the guanacoite to the department 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 additional anions to the phosphate, arsenate or vanadate complex, so that the mineral can be classified according to its composition in the subsection “With only medium-sized cations; (OH etc.): RO 4 = 2: 1 ”, where together with the eponymous acrochordite he forms the“ acrochordite group ”with the system no. 8.DD.10 forms.
The systematics of minerals according to Dana , which is common in the English-speaking world , assigns the guanacoite to the division of “hydrated phosphates etc., with hydroxyl or halogen” and there in the sub-division of “ hydrated phosphates etc., with hydroxyl or halogen and the general composition (AB ) 5 (XO 4 ) 2 Z q • x (H 2 O) “, where it also forms the unnamed group 42.04.01 together with acrochordite .
Chemism
The chemical composition determined with the help of electron beam microanalysis showed a percentage by weight of 29.67% CuO , 17.12% MgO , 35.67% As 2 O 5 and 18% H 2 O. This corresponds to the empirical formula Cu 2.32 Mg 2.64 (OH ) 4.13 (H 2 O) 4.15 (AsO 4 ) 1.93 or simplified Cu 2 Mg 2 (Mg 0.5 Cu 0.5 ) (OH) 4 (H 2 O) 4 (AsO 4 ) 2 .
Crystal structure
Guanacoite crystallizes isotypically with acrochordite in the monoclinic crystal system in the space group P 2 1 / c with the lattice parameters a = 5.459 (2) Å ; b = 16.808 (9) Å; c = 6.917 (3) Å and β = 100.44 (1) ° as well as two formula units per unit cell .
Education and Locations
Since all guanacoite samples were found on the spoil heaps of the Guanaco opencast mine, the exact position of the occurrence within the mine field is not known. The El Guanaco deposit itself was created under hydrothermal conditions at rather low temperatures between 200 and 100 ° C ( epithermal ) with a high degree of sulphidation . Acid-related alterations (mineral transformations) and weathering processes led to an enrichment of various metals and thus, in addition to native copper , gold and silver, also to the formation of a large number of corresponding, sometimes rare minerals such as arhbarite , brochantite , chenevixite (Cu 2 Fe 3+ 2 [(OH ) 2 | AsO 4 ] 2 ), chrysocolla , enargite , Klinoklas , Konichalcit , Lammerit , Lavendulan , Lemanskiit and Olivenit and Jodargyrit and Bismoclit (BiOCl) led.
In addition to the El Guanaco pits in Chile and Taghouni in Morocco, only one other site for guanacoite is known to date (as of 2017), namely the Cerro de la Corona in Spain near Huércal de Almería in Andalusia .
See also
literature
- Thomas Witzke, Uwe Kolitsch, Werner Krause, Annemarie Wiechowski, Olaf Medenbach, Anthony R. Kampf, Ian M. Steele, Georges Favreau: Guanacoite, a new arsenate mineral species from the El Guanaco Mine, near Taltal, Chile: Description and crystal structure . In: European Journal of Mineralogy . tape 18 , no. 6 , 2006, p. 813-821 , doi : 10.1127 / 0935-1221 / 2006 / 0018-0813 ( rruff.info [PDF; 329 kB ; accessed on September 22, 2019]).
- Atsushi Kyono: Compositional variability and crystal structural features of guanacoite . In: American Mineralogist . tape 93 , 2008, p. 501–507 ( rruff.info [PDF; 1,2 MB ; accessed on September 22, 2019]).
Web links
- Mineral Atlas: Guanacoite (Wiki)
- Guanacoite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on September 22, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Guanacoite. In: rruff.geo.arizona.edu. Retrieved September 22, 2019 .
Individual evidence
- ↑ a b c d Thomas Witzke, Uwe Kolitsch, Werner Krause, Annemarie Wiechowski, Olaf Medenbach, Anthony R. Kampf, Ian M. Steele, Georges Favreau: Guanacoite, a new arsenate mineral species from the El Guanaco Mine, near Taltal, Chile : Description and crystal structure . In: European Journal of Mineralogy . tape 18 , no. 6 , 2006, p. 813-821 , doi : 10.1127 / 0935-1221 / 2006 / 0018-0813 ( rruff.info [PDF; 329 kB ; accessed on January 22, 2018]).
- ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
- ↑ David Barthelmy: Guanacoite Mineral Data. In: webmineral.com. Retrieved September 22, 2019 .
- ↑ a b c Atsushi Kyono: Compositional variability and crystal structural features of guanacoite . In: American Mineralogist . tape 93 , 2008, p. 501–507 ( rruff.info [PDF; 1,2 MB ; accessed on September 22, 2019]).
- ^ Mineral Atlas: Guanacoite
- ↑ a b c d e Guanacoite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 22, 2019 .
- ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: September 2019. (PDF 2672 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed on September 22, 2019 .
- ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 22, 2019 .
- ↑ Find location list for guanacoite in the Mineralienatlas and Mindat