The surface mineralisation at BEP and BWP comprises chalcocite, covellite and digenite
mineralisation with lesser chalcopyrite.
Copper sulphides such as CuS (covellite), [Cu.sub.1.75]S (anilite), [Cu.sub.1.8]S (digenite
), [Cu.sub.1.95]S (djurlite), and [Cu.sub.2]S are of great interest as they can be applied in energy storage, owing to their variations in stoichiometric compositions, complex structures, and valence states .
There are five stable phases of [Cu.sub.x]S at room temperature which vary according to values of x (1 [less than or equal to] x [less than or equal to] 2): chalcocite ([Cu.sub.2]S), djurleite ([Cu.sub.1.95]S), digenite
([Cu.sub.1.8]S), anilite ([Cu.sub.1.75]S), and covellite (CuS) [8, 9].
It was concluded that tetrahedrite decomposes into iron (or zinc) rich tetrahedrite, antimony, famatinite, and digenite
. It was also reported that the Cu-Sb-S alloy system is less stable compared to the iron (or zinc) bearing CAS alloy system at room temperature .
Minerals associated with cubic magnetite at Balmat, New York Anhydrite [CaSO.sub.4] Arsenopyrite FeAsS Atacamite [Cu.sub.2][Cl(OH).sub.3] Betekhtinite [Cu.sub.10](Pb,Fe)[S.sub.6] Bornite [Cu.sub.5][FeS.sub.4] Bottallackite [Cu.sub.2]Cl[(OH).sub.3] Calcite [CaCO.sub.3] Celestine [SrSO.sub.4] Chalcocite [Cu.sub.2]S Chalcopyrite [CuFeS.sub.2] Digenite
[Cu.sub.9][S.sub.5] Galena PbS Gordaite [NaZn.sub.4]([SO.sub.4])[(OH).sub.6]Cl*6[H.sub.2]O Halite NaCl Hematite [Fe.sub.2][O.sub.3] Malachite [Cu.sub.2]([CO.sub.3])[(OH).sub.2] Nantokite CuCl Namuwite [(Zn,Cu).sub.4][SO.sub.4][(OH).sub.6]*4[H.sub.2]O Paratacamite [Cu.sub.2]Cl[(OH).sub.3] Pyrite [FeS.sub.2] Silver Ag Sphalerite ZnS Talc [Mg.sub.3][Si.sub.4][O.sub.10][(OH).sub.2] Crystal Sizes
The powder diffraction pattern was consistent with the digenite
phase of copper sulfide that has a stoichiometry of [Cu.sub.9][S.sub.5] or [Cu.sub.1.8]S.
Dominant sulphide minerals are chalcopyrite, pyrite and bornite with subordinate chalcocite and digenite
. Sulphide content is low, averaging less than 1% overall.
Today the Butte mines are closed and flooded, but its mineralogical legacy of fine specimens remains--most noteably the copper sulfide and sulfosalt minerals such as bornite, chalcocite, chalcopyrite, colusite, covellite, digenite
, djurleite, and enargite, and other minerals such as barite, pyrite, quartz and silver.
The predominant economic sulphide minerals are chalcocite, digenite
, bornite, carrollite and chalcopyrite.