Sulphides: Bournonite
Diagnostic card.
Pb Cu Sb S 3
Diamond orthogonality
Hardness 2,5-3
Specific weight 5,7-5,9
Cleavage imperfect
Cracked shell
Color gray, black
Color in powder gray
Glitter metal
Bournonite, copper, lead and antimony sulphide. The gloss is metallic, opaque. Colors: from gray-steel to iron-black. The line is gray. The fracture is conchoidal, uneven. It's fragile. Cleavage is imperfect.
It forms in hydrothermal veins. Crystals (rhombic syngony) are thick-plate. Aggregates are usually dense, drained or granular.
Due to the similarity of twin splices with cogwheels, burnite is also called "wheel ore". Important copper-lead ore. Places of distribution: Germany, Austria, England, Mexico, Peru, Bolivia, USA, Canada, CIS.
One of the most common representatives of sulphosalts, highly appreciated by collectors due to its characteristic twin crystals, which are often accompanied by fine druses of tetrahedrite, sphalerite, chalcopyrite, galena, pyrite, siderite, quartz, antimonite, zincite, rhodochrosite, dolomite, barite, etc. Crystals of burnonite are tabular, prismatic with shading, and also difficultly twinned. The color is steel-gray and iron-black.
Bourbonite on white quartz. Yaogangxian Mine, Hunan, Chin. (2011).
Chemical composition. Copper (Cu) 13.0%, lead (Pb) 42.4%, antimony (Sb) 24.9%, sulfur (S) 19.7% (copper, lead, antimony sulfide). The shape of the crystals. Well-formed crystals; Pseudotetragonal, short-prismatic or thick-plate crystals; There are twins, often polysynthetic, in the form of a cross or a wheel. Crystal structure. Not yet studied. Class of symmetry. Rhombo-pyramidal-mm2. Cleavage. Distinct, parallel to the axis with (010). Aggregates. Wrong grain, solid masses.
Diagnostic signs.
It dissolves in nitric acid. From the presence of copper, the solution becomes green. It melts at low temperature. Steel gray, dark gray, with topakovo-brown tingling. It easily melts on coal with the formation of a lead-copper ball. Behavior in acids. Soluble in HNO3 with precipitation of sulfur and antimony oxide (Sb2O3).
Origin.
Occurs in veins with galena, sphalerite and various sulfosalts.
Deposits and applications.
Known mainly in the fields of Germany and the Czech Republic, Hungary, Romania, in numerous areas of the USA, Bolivia, Peru and Chile. In Italy it is quite common. Bournonite, together with siderite and quartz, is found in Brosso and Borgofranco near Ivrea, in marbles of Carrara and in Val di di Castello (Pietrasanta, Lucca), in the form of dense concretions in the lead-zinc mine of Bergamasco. Used to extract copper, lead and antimony.
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Poisonous and radioactive dangerous stones and minerals
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Catalog of minerals and semi-precious stones of the world by groups
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