Lafossait
| Lafossait | |
|---|---|
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|
| General and classification | |
| other names |
IMA 2003-032 |
| chemical formula | TlCl |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.AA.25 ( 8th edition : III / A.04) 01/09/03/02 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | Pm 3 m (No. 221) |
| Lattice parameters | a = 3.8756 (3) Å |
| Formula units | Z = 1 |
| Frequent crystal faces | {100}, {111} |
| Physical Properties | |
| Mohs hardness | 3 to 4 |
| Density (g / cm 3 ) | calculated: 7.212 |
| Cleavage | slightly mussel-like |
| colour | gray-brown |
| Line color | creamy white |
| transparency | translucent |
| shine | Resin to greasy gloss |
| Crystal optics | |
| Refractive index | n = 2.264 |
| Other properties | |
| Chemical behavior | soluble in dilute hydrochloric acid |
Lafossaite is a very rarely occurring mineral from the mineral class of halides . It crystallizes in the cubic crystal system with the idealized chemical composition TlCl and is therefore chemically thallium (I) chloride .
So far, Lafossaite could only be found in the form of microscopic to a few millimeters large, ingrown , cubic crystals of gray-brown color.
Etymology and history
The mineral was first discovered as a crusty druse filling on an active fumarole at the “La Fossa” crater on Vulcano ( Aeolian Islands ). The name of the mineral refers to its type locality .
Lafossaite was recognized as a mineral by the International Mineralogical Association (IMA) as early as 2003 under the entry no. IMA 2003-032 . Although the name was also recognized in this process, it was not published until 2006 together with the results of the analysis of the mineral by its first descriptors AC Roberts, KE Venance, TM Seward, JD Grice and WH Paar.
Type material of the mineral is in the research collection of TM Seward at the Institute for Mineralogy and Petrography of the ETH Zurich in Switzerland, in the systematic reference series of the National Mineralogical Collection of Canada of the Geological Survey of Canada in Ottawa under the catalog no. # 68098 and in the Natural History Museum in London under catalog no. BM2004,55 kept.
classification
Already in the outdated, but still in use 8th edition of the mineral classification according to Strunz , the lafossaite belonged to the mineral class of "halides" and there to the department of "simple halides", where it formed the unnamed group III / A.04 together with ammonia .
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the Lafossaite in the already more finely subdivided division of "simple halides without H 2 O". This is further subdivided according to the molar ratio of metal to halide in the formula, so that the mineral is to be found according to its composition in the sub-section "M: X = 1: 1 and 2: 3", where together with ammonia it forms the "ammonia group “With the system no. 3.AA.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Lafossaite to the class and division of the same name of "halides". Here it can be found in the unnamed group 09.01.03 within the sub-section "Anhydrous and hydrous halides with the formula AX".
Crystal structure
Lafossaite crystallizes in the cubic crystal system in the space group Pm 3 m (space group no. 221) with the lattice parameter a = 3.8756 (3) Å and one formula unit per unit cell .
Education and Locations
Lafossaite previously appeared as a kidney-shaped layer on the surface of individual specimens, where it had formed as a sublimation product of escaping volcanic gases. Cannizzarite , galenobismutite and pyrite appeared there as accompanying minerals .
In addition to its type locality, the “La Fossa” crater on Vulcano, Lafossait could also be discovered in Italy on Vesuvius in the province of Naples. Furthermore, the mineral is only known from the Xiangquan thallium deposit in the Chinese prefecture of Ma'anshan , from Mount Nakalak in the Ilímaussaq massif near Narsaq (Kitaa district) on Greenland and possibly from the Marcel mine near Radlin in the Polish voivodeship Silesia .
See also
literature
- Andrew C. Roberts, Katherine E. Venance, Terry M. Seward, Joel D. Grice, Werner H. Paar: Lafossaite, a new mineral from the La Fossa Crater, Vulcano, Italy . In: The Mineralogical Record . tape 37 , 2006, p. 165–168 ( abstract at highbeam.com [accessed May 27, 2017]).
- Paula C. Piilonen, Ralph Rowe, T. Scott Ercit, Andrew J. Locock: New Mineral Names . In: American Mineralogist . tape 91 , 2006, p. 1452-1457 , doi : 10.2138 / am.2006.470 ( minsocam.org [PDF; 137 kB ; accessed on May 27, 2017] Lafossait from p. 1455).
Web links
- Mineral Atlas: Lafossaite (Wiki)
- Thomas Witzke : Mineral Photo Atlas. Lafossait at www.strahl.org
- American-Mineralogist-Crystal-Structure-Database - Lafossaite (English)
Individual evidence
- ↑ Webmineral - Lafossaite (English)
- ^ A b c d Andrew C. Roberts, Katherine E. Venance, Terry M. Seward, Joel D. Grice, Werner H. Paar: Lafossaite, a new mineral from the La Fossa Crater, Vulcano, Italy . In: The Mineralogical Record . tape 37 , 2006, p. 165–168 ( abstract at highbeam.com [accessed May 27, 2017]). Abstract at www.highbeam.com ( Memento of the original from November 19, 2018 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c d Lafossaite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 114 kB ]).
- ↑ Mindat - Lafossaite (English)
- ↑ Find location list for Lafossaite at the Mineralienatlas and at Mindat
