Boulangerite

BOULANGERITE (from the name of the French Mining engineer Charles L. Boulanger * EN: boulangerite; DE: Boulangent; FR: boulangerite; ES: bulangerita; RU: буланжерит) is the mineral of the class of the complex sulfides (sulfosalts), Pb5Sb4S11. It contains: Pb - 58.9%, Sb - 22.8%, S - 18.3%. It crystallizes itself into the monoclinic crystal system. The structure is of the chain-ribbon type. It may be found mainly in the form of the aggregates of the radiant and thin fibrous structure, less often in the form of the acicular, columnar, and tabular crystals. The colour is from lead-gray to iron-black. The lustre is metallic, the cleavage is average along the (100) plane. The density is 6230 kilograms per cubic metre. The hardness is 2.5-3.0. It is brittle, opaque, good conductor for electricity. It may be found as the secondary mineral within the hydrothermal deposits, together with other complex sulfides of lead, galena, antimonite, sphalerite, pyrite, fahlores. Within the USSR, it is characteristic for the series of deposits within Transbaikalia, Uzbekistan, and Ukraine. Abroad, it is known within Czechoslovakia, East Germany, France, Sweden, USA. It serves as the secondary lead ore. It is beneficiated by flotation, with the usage of xanthates with other sulfides of lead and copper.