Playfairite
- IMA 1966-019
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 Pb16V (Sb, As) 19S44Cl given in the parentheses elements antimony and arsenic can relax in the formula each represent each other (substitution, Diadochie ), but are always in the same proportions to the other components of the Minerals.
Playfairit is opaque and developed tabular and along the longitudinal axis of strong striped crystals of lead- gray to black in color with black stroke color.
Etymology and history
Was first discovered in the quarry Playfairit " Taylor " 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In the now outdated but still in use 8th edition of the mineral classification by Strunz the Playfairit belonged to the department of the " sulpho (S: As, Sb, Bi = x) ", where he and along with Dadsonit, Launayit, Madocit, Pellouxit, Sorbyit Sterryit the unnamed group II/E.20 formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Playfairit in the new department of " unclassified sulfosalts " one. This is further subdivided according to the possible presence of lead ( Pb), so that the mineral is found according to its composition in the subsection " Pb ", where it forms the unnamed group 2.LB.55 the only member.
The mainly common in English-speaking classification of minerals according to Dana assigns the Playfairit in the class of " sulfides and sulfosalts " and there in the department of " thio " one. Here he is the only member of the unnamed group 03.06.04.01 within the subdivision of the " sulpho with the ratio 2.0 < z / y < 2.49, and the composition (A ) i ( A2 ) j [ Bycz ], A = to find metals, semimetals B =, C = non-metals ".
Education and Locations
Playfairit can be found in the form of massive aggregates in small veins that run through dolomitic and calcitic marbles. It is formed at the edges of other sulfosalts and penetrates through microscopic cracks or veins in this one. Accompanying minerals occur among others orpiment, antimony Baumhauerit, Boulangerite, Cinnabar, fluorite, galena, Geokronit, Guettardit, Jamesonite, Launayit, Madocit, pyrite, quartz, realgar, Robinsonit, Semseyit, Sorbyit, sphalerite, and Twinnit Zinkenite.
Except at its type locality in the quarry " Taylor " in Canada Playfairit has so far (as of 2013) only in the pit " Les Cougnasses " at Orpierre in the French Alps, in the antimony - mercury deposit Khaidarkan ( Chaidarkan ) in the Ferghana Valley in Kyrgyzstan and are found at the Reese River in Lander County in the U.S. state of Nevada.
Crystal structure
Playfairit monoclinic with lattice parameters a = 45.4 Å; b = 8.29 Å; c = 21.3 Å and 92.5 ° β = and 8 formula units per unit cell.