Playfairit
| Playfairit | |
|---|---|
| General and classification | |
| other names |
IMA 1966-019 |
| chemical formula | Pb 16 (Sb, As) 19 S 44 Cl |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.LB.55 ( 8th edition : II / E.20) 06/03/04/01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | Please complete |
| Lattice parameters |
a = 45.4 Å ; b = 8.29 Å; c = 21.3 Å β = 92.5 ° |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | not defined ( Vickers hardness : VHN 50 = 154 kg / mm 2 ) |
| Density (g / cm 3 ) | calculated: 5.72 |
| Cleavage | completely after {100} |
| colour | lead gray to black |
| Line color | black |
| transparency | opaque |
| shine | Metallic luster |
Playfairit is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the monoclinic crystal system with the composition Pb 16 (Sb, As) 19 S 44 Cl.The elements antimony and arsenic indicated in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion the other components of the mineral.
Playfairit is opaque and develops tabular crystals, strongly striped along the longitudinal axis, from lead-gray to black in color with black streak color .
Etymology and history
Playfairite was first discovered in the "Taylor" quarry near Huntingdon in Hastings County in the Canadian province of Ontario and described in 1967 by John Leslie Jambor (1936-2008), who named the mineral after the Scottish mathematician and geologist John Playfair .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Playfairit belonged to the department of "sulfosalts (S: As, Sb, Bi = x)" where he collaborated with Dadsonit , Launayit , Madocit , Pellouxit , Sorbyit and Sterryit formed the unnamed group II / E.20 .
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 Playfairit in the new section of "unclassified sulfosalts". This is further subdivided according to the possible presence of lead (Pb), so that the mineral can be found according to its composition in the sub-section "with Pb", where it is the only member of the unnamed group 2.LB.55 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Playfairit to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here he is the only member of the unnamed group 06/03/04/01 within the subdivision of “ Sulphosalts with the ratio 2.0 <z / y <2.49 and the composition (A + ) i (A 2+ ) j [B y C z ], A = metals, B = semimetals, C = non-metals ”.
Education and Locations
Playfairit is found in the form of massive aggregates in small veins that run through dolomitic and calcitic marbles. It forms on the edges of other sulfosalts and penetrates them through microscopic cracks or veins. As Begleitminerale occur among other orpiment antimony, Baumhauerit , Boulangerit , Cinnabar , fluorite , galena , Geokronit , Guettardit , Jamesonit , Launayit , Madocit , pyrite , quartz , realgar , Robinsonit , Semseyit , Sorbyit , sphalerite , Twinnit and Zinkenite on.
Apart from its type locality in the “Taylor” quarry in Canada, Playfairit has so far only been able to (as of 2013) in the “Les Cougnasses” mine near Orpierre in the French Alps, in the Khaidarkan (Chaidarkan) antimony-mercury deposit in the Ferghana Valley in Kyrgyzstan and on the Reese River in Lander County , Nevada, USA.
Crystal structure
Playfairite crystallizes monoclinically with the lattice parameters a = 45.4 Å ; b = 8.29 Å; c = 21.3 Å and β = 92.5 ° and 8 formula units per unit cell .
See also
literature
- JL Jambor: New lead sulfantimonides from Madoc, Ontario; Part 2, Mineral descriptions , in: The Canadian Mineralogist , Volume 9/2 (December 1967), pp. 191-213
Web links
Individual evidence
- ↑ a b IMA / CNMNC List of Mineral Names 2012 (PDF 8.5 MB)
- ^ A b Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 135 .
- ↑ a b c d Playfairite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 63.4 kB )
- ^ Mindat - Playfairite