Tree strength
| Tree strength | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1999-049 |
| chemical formula | Ag 3 (Sb, As) 2 SbS 6 (idealized AgSbS 2 ) |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.HA.25 ( 8th edition : II / C.16) 07/03/04/02 |
| Similar minerals | Galena , aramayoite |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic-pinacoidal 1 |
| Space group | P 1 |
| Lattice parameters |
a = 7.766 Å ; b = 8.322 Å; c = 8.814 Å α = 100.62 °; β = 104.03 °; γ = 90.22 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {001}, {10 1 }, {201}, {010}, {01-1}, {100} |
| Twinning | after {001} |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | measured: 5.33; calculated: 5.39 |
| Cleavage | completely after {001} |
| colour | iron black, brownish black |
| Line color | grey black |
| transparency | opaque |
| shine | Metallic luster |
Tree starch is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the triclinic crystal system with the composition Ag 3 (Sb, As) 2 SbS 6 (idealized AgSbS 2 ), so it is chemically a silver - antimony- sulfide.
Baumstarkit only develops small, isometric crystals up to about 3 mm in size with a silver metallic sheen , but iron-black to brownish-black tarnish and gray-black streak color .
Etymology and history
The mineral is named after the German mineralogist Manfred J. Baumstark (* 1954), who provided some mineral samples from the "San Genaro Mine" near Castrovirreyna ( Huancavelica region , Peru) for study purposes and who suggested new analyzes, since in the San Genaro Mine no other Bi-containing minerals occur. Until then, the material found in the early 1980s had been inappropriately referred to as aramayoite (Ag (Sb, Bi) S 2 ) for almost 20 years .
Herta Effenberger and Michel Fleck from Vienna, Werner Hermann Paar and Dan Topa from Salzburg and Alan J. Criddle from London formed a research group in order to be able to analyze the mineral and prepare a scientific description. The results and the name chosen by them in honor of the German mineralogist Baumstark were submitted to the International Mineralogical Association (IMA) for examination in 1999 (register no. IMA 1999-049 ). In the same year, Baumstarkit was recognized as an independent mineral. In 2002 the research results and the recognized name were published in the American Mineralogist .
classification
In the meanwhile outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the tree starch belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio of metal: sulfur, selenium, tellurium = 1: 1", where, together with aramayoite, bohdanowiczite , cuboargyrite , matildite , miargyrite , schapbachite and volynskite, the independent group II / C.16. educated.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns tree starch to the class of "sulfides and sulfosalts", but in the department of "sulfosalts with SnS as a model". This section is further subdivided according to the cations involved in the chemical structure , so that the mineral can be found according to its composition in the sub-section “With Cu, Ag, Fe (without Pb)”, where it is the unnamed group only together with aramayoite 2.HA.25 forms.
The systematics of minerals according to Dana also assigns tree starch to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here it is also together with aramayoite in the unnamed group 07/03/04 within the subsection “ Sulphosalts with the ratio z / y = 2 and the composition (A + ) i (A 2+ ) j [B y C z ], A = Metals, B = semi-metals, C = non-metals ”.
Modifications and varieties
The compound AgSbS 2 is trimorphic , so besides the triclinic tree starch it also occurs as cubic crystallizing cuboargyrite and as monoclinic crystallizing miargyrite .
Education and Locations
Tree starch forms under hydrothermal conditions. Besides miargyrite, accompanying minerals include andorite , chalcopyrite , diaphorite , galena , kesterite , pyrargyite , pyrite , robinsonite , sphalerite and stannite .
In addition to its type locality “San Genaro Mine” in Peru, the mineral could also be found in the “Santiago Alto Mine” near Porco and the “Chocaya Mine” near Atocha- Quechisla in the Bolivian Department of Potosí , the “Gabe Gottes Mine” near Sainte-Marie- aux mines in France and in the "Koryu Mine" in the Japanese province of Ishikari .
Crystal structure
Baumstarkite crystallizes isotypically with aramayoite in the triclinic crystal system in the space group P 1 with the lattice parameters a = 7.766 Å ; b = 8.322 Å; c = 8.814 Å; α = 100.62 °; β = 104.03 ° and γ = 90.22 ° as well as 2 formula units per unit cell .
See also
Individual evidence
- ↑ a b c d e Effenberger et al .: The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite
- ↑ Webmineral - Baumstarkite (English)
- ↑ Manfred Baumstark: baumstark-mineralien.com - Comments on the new silver mineral Baumstarkit ( Memento from January 17, 2013 in the web archive archive.today )
- ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 978-3-921656-70-9 , p. 31 .
- ↑ Mindat - Baumstarkite (English)
literature
- Herta Effenberger, Werner Hermann Paar, Dan Topa, Alan J. Criddle, Michel Fleck: The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite , in: American Mineralogist , Volume 87, pp. 753-764, 2002, doi: 10.2138 / am-2002-5-619 ( English, PDF 428 kB )
- John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, and Monte C. Nichols (2011): Baumstarkite , in: Handbook of Mineralogy , Mineralogical Society of America ( English, PDF 63 kB )
Web links
- Mineral Atlas: Baumstarkit (Wiki)