Boulangerite
Boulangerite is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ." It crystallizes in the orthorhombic crystal system with the chemical composition Pb5Sb4S11 and usually develops granular or fibrillar aggregates, but also rarely acicular, striped crystals of gray-black color with black stroke color.
Boulangerite is opaque and shows in crystalline form a metallic luster, with fibrous aggregates, however, silky shine. Its Mohs hardness varies from 2.5 to 3, can thus be of a fingernail barely, with a copper coin, however, have yet to scratch.
Etymology and history
Was first discovered Boulangerite in the municipality of Molière in the French department of Gard and analyzed initially by Charles Louis Boulanger (1810-1849), a French mining engineer, and in 1837 again by Thaulow, the analysis of a content of 18.86 % sulfur, 24, 60 % antimony and 55.57 % of lead found. After Boulanger, the mineral was then named.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Boulangerite belonged to the mineral class of " sulfides and sulfosalts " and there to the general ward of " thio ", where he and along with Ardait, Falkmanit, Jaskolskiit, Moëloit, Pillait Plumosit an independent group formed.
The valid since 2001 and used by the IMA 9th edition of the Strunz'schen Mineral classification assigns the Boulangerite in the extended class of " sulfides and sulfosalts ( sulfides, selenides, tellurides, arsenides, antimonides, bismuthides, Sulfarsenite, Sulfantimonite, Sulfbismuthite ) " and there in the department of " sulfosalts with SnS as a role model ." This division, however, is further subdivided according to the nature of the cations involved, so that the mineral is found according to its composition in the subsection "Only with lead ( Pb) " where there is only together with Falkmanit and Plumosit the unnamed group 2.HC .15 forms.
The classification of minerals according to Dana assigns the Boulangerite in the class of " sulfides and sulfosalts " and there in the department of " thio ". Here he is with Falkmanit in the unnamed group 03:05:02 within the subdivision of the " sulpho with the ratio of 2.5 < z / y < 3 and the composition (A ) i ( A2 ) j [ Bycz ], where A = metals to find B = semimetals, C = non-metals ".
Education and Locations
Boulangerite formed by hydrothermal processes at low to medium temperatures. Accompanying minerals include various lead sulfides and sulfosalts such as arsenopyrite, galena, pyrite, sphalerite and stibnite, but also siderite and quartz.
Worldwide, Boulangerite so far (as of 2010) are detected at around 600 localities, so include Afghanistan, Egypt, Argentina, Armenia, Australia, Bolivia, Bulgaria, Chile, China, Germany, Ecuador, Finland, France, Georgia, Ghana, Greece, Greenland, India, Indonesia, Iran, Ireland, Italy, Japan, Kazakhstan, Kyrgyzstan, Colombia, North and South Korea, Croatia, Malaysia, Morocco, Macedonia, Mexico, Mongolia, Namibia, Norway, Austria, Peru, Poland, Romania, Russia, Sweden, Switzerland, Serbia, Slovakia, Slovenia, Spain, South Africa, Czech Republic, Ukraine, Hungary, the United Kingdom ( UK ) and the United States of America (USA).
Crystal structure
Boulangerite crystallizes in the orthorhombic space group Pnam with the lattice parameters a = 23.49 Å; b = 21.24 Å and c = 4.02 Å and four formula units per unit cell.