Zaherite
| Zaherite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1977-002 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Sulphates (selenates, tellurates, chromates, molybdates and tungstates) |
|
System no. to Strunz and to Dana |
7.DE.65 ( 8th edition : VI / D.06) 10/31/03/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triklin-pedial; 1 or triclinic pinacoidal; 1 |
| Space group | P 1 (No. 1) or P 1 (No. 2) |
| Lattice parameters |
a = 18.47 Å ; b = 19.45 Å; c = 3.77 Å α = 95.2 °; β = 91.5 °; γ = 80.2 ° |
| Formula units | Z = 1 |
| Physical Properties | |
| Mohs hardness | ≈ 3.5 |
| Density (g / cm 3 ) | measured: 2.007 to 2.011; calculated: 2.01 |
| Cleavage | Well |
| colour | colorless, chalk white to light bluish green |
| Line color | White |
| transparency | translucent |
| shine | Pearlescent, earthy matt |
| Crystal optics | |
| Refractive indices |
n α = 1.498 n β = 1.498 n γ = 1.499 |
| Birefringence | δ = 0.001 |
| Optical character | biaxial positive |
| Axis angle | 2V = 38 ° (calculated) |
Zaherite is a very rarely occurring minerals from the mineral class of "sulfates" with the chemical composition Al 12 [(OH) 26 | (SO 4 ) 5 ] · 20H 2 O and chemical point of view, a hydrous aluminum - sulfate with additional hydroxide .
Zaherite crystallizes in the triclinic crystal system , but develops only microscopic, fibrous to tabular crystallites of a few hundred micrometers and so far could only be found in the form of dense and extremely fine-grain mineral aggregates with a wavy texture. In its pure form, Zaherite is colorless and transparent. Due to the multiple refraction of light due to the polycrystalline formation, however, it usually appears translucent, chalky white and can take on a light bluish green color due to foreign admixtures. The surfaces of the Zaherit aggregates have a mother-of-pearl shine or are earthy-matt.
Etymology and history
Zaherit was first discovered in 1969 by Mohammed Abduz Zaher (* 1935) from the Geological Survey of Bangladesh in clay mineral samples from the salt mountains of the Pakistani province of Punjab . In his unpublished master’s thesis, he presented the results of his research and, based on the X-ray diffraction data, postulated a new mineral, which he regarded as hydrous aluminum silicate or oxide.
A first complete analysis was carried out by AP Routsala and LL Babcock, who named the new mineral Zaherite in honor of its discoverer. Routsala and Babcock submitted their test results and the chosen name for examination to the International Mineralogical Association (IMA), which it received with the internal receipt no. 1977-002 recognized as an independent mineral type in the same year. The first description was published in the same year in the American Mineralogist magazine .
The type material of the mineral is in the National Museum of Natural History in Washington, DC (USA) under the catalog no. 143793 kept.
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the zaherite belonged to the mineral class of "sulfates, chromates, molybdates, tungstates" (including selenates and tellurates) and there to the department of "hydrous sulfates with foreign anions ", where he, along with aluminide , Felsőbányait , Hydrobasaluminit , Jurbanite , Khademit , meta Aluminite and Rostit the "Aluminite group" with the system number. VI / D.06 .
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, also assigns zaherite to the class of "sulfates (selenates, tellurates, chromates, molybdates and tungstates)" and then to the department of "sulfates (selenates, etc.) .) with additional anions, with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the crystal structure, so that the mineral is classified in the sub-section “With only medium-sized cations; unclassified ”can be found, where it is the only member of the unnamed group 7.DE.65 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns zaherite to the class of "sulfates, chromates, molybdates" and there in the category of "water-containing sulfates with hydroxyl or halogen". Here he is to be found as the only member in the unnamed group October 31, 2003 within the sub-section “ Various hydrous sulfates with hydroxyl or halogen ”.
Crystal structure
Zaherite crystallizes triclinically in the space group P 1 (space group no. 1) or P 1 (no. 2) with the lattice parameters a = 18.47 Å ; b = 19.45 Å; c = 3.77 Å; α = 95.2 °; β = 91.5 ° and γ = 80.2 ° and one formula unit per unit cell .
Education and Locations
At its type locality in the salt mountains of Punjab, Pakistan, Zaherite was found in small mineral veins that run through the rocks containing kaolinite , boehmite and aluminite .
In open pit Hotson 6 , a sillimanite -Grube about 65 kilometers west of Pofadder in Bosmanland the South African Northern Cape is formed Zaherite accompanied by Hotsonit as a conversion product of natroalunite or by hydrothermal sulfation of sillimanite.
The only other known site (as of 2018) for Zaherite is the Grotta dell'Allume on the Italian island of Vulcano off the north coast of Sicily .
See also
literature
- AP Routsala, LL Babcock: Zaherite, a new hydrated aluminum sulfate . In: American Mineralogist . tape 62 , no. 11-12 , 1977, pp. 1125 – l128 (English, minsocam.org [PDF; 285 kB ; accessed on January 7, 2019]).
- Aylva E. Schoch, Gerhard J. Beukes, Hermann E. Praekelt: A natroalunite-zaherite-hotsonite paragenesis from Pofadder, Bushmanland, South Africa . In: The Canadian Mineralogist . tape 23 , no. 1 , 1985, pp. 29–34 (English, rruff.info [PDF; 718 kB ; accessed on January 7, 2019]).
- H. De Bruiyn, AE Schoch, GJ Beukes, LDC Bok, WA Van der Westhuizen: Note on cell parameters of zaherite . In: Mineralogical Magazine . tape 49 , 1985, pp. 145–146 , doi : 10.1180 / minmag.1985.049.350.26 (English, rruff.info [PDF; 100 kB ; accessed on January 7, 2019]).
- Pete J. Dunn , George Y. Chao, Joan J. Fitzpatrick, Richard H. Langley, Michael Fleischer , Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 71 , no. 1-2 , 1986, pp. 227–232 (English, minsocam.org [PDF; 765 kB ; accessed on January 7, 2019] Zaherite from p. 231).
Web links
- Mineral Atlas: Zaherite (Wiki)
- David Barthelmy: Zaherite Mineral Data. In: webmineral.com. Retrieved January 7, 2019 .
Individual evidence
- ^ IMA / CNMNC List of Mineral Names; November 2018 ( Memento from March 23, 2019 in the Internet Archive ) (PDF 1.7 MB)
- ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 400 (English).
- ↑ a b Zaherite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 67 kB ; accessed on January 7, 2019]).
- ↑ a b 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 .
- ↑ a b c d e Zaherit. In: mindat.org. Hudson Institute of Mineralogy, accessed January 7, 2019 .
- ↑ Catalog of type mineral specimens of the Commission on Museums (IMA) - Z ( Memento from September 14, 2016 in the Internet Archive ) (English, PDF 29 kB)
- ↑ Find location list for Zaherite at the Mineralienatlas and at Mindat