Digenite
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Digenite is a copper sulfide mineral with formula: Cu 9 S 5 . Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal–hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits.
Digenite is a copper sulfide mineral with formula: Cu 9 S 5 . Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal–hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits. High digenite is stable above 73 °C, with space group Fm m and unit cell parameters a = 5.57 Å and Z = 1 for formula Cu 7.2−x S 4 . High digenite is isostructural with bornite Cu 5 FeS 4 . Metastable digenite forms on cooling from 73 °C. It appears to be isometric with space group Fd m and a = 27.85 Å. This symmetry, however, is due to twinning of fine domains with rhombohedral symmetry, trigonal -3m, point group R-3m, a = 3.92 Å, c = 48 Å, Z = 15 for formula Cu 1.8 S. Metastable digenite changes with time to stable low temperature digenite or a mixture of anilite Cu 7 S 4 and djurleite Cu 31 S 16 . Low digenite is isometric, space group Fd m and a = 27.85 Å, i.e. the same as the apparent isometric symmetry of the metastable polymorph, Z=4 for formula Cu 1.8 S. ==References== Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7th edition), v. I, pp. 180–182.
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