Cubanite

Fig. 7-13. An example of a semiquantitati e application of the curved-crystal x-ray spectrometer used by Adler and Axelrod. By using chalcopyrite (CuFeS2) as a standard, the proper atomic ratios of copper to iron were obtained for bornite (Cu5FeS4) and cubanite (CuFe2S3). The Cu/Fe weight ratios in these minerals are 1.14 (chalcopyrite), 5.69 (bornite), and 0.57 (cubanite). (Courtesy of Adler and Axelrod, Norelco Reptr., 3, 65.)...

Cubanite, analysis by x-ray emission spectrography, 207, 208 Curved-crystal arrangement, evaluation, 123, 124... 

Main opaque minerals include native gold, electrum, pyrite, pyrrhotite, chalcopy-rite, cubanite, sphalerite, arsenopyrite and tellurobismutite. The amounts of these sulfide minerals are poor, compared with those in epithermal Au-Ag vein-type deposits. It is noteworthy that silver minerals are abundant in epithermal Au-Ag vein-type deposits, whereas they are poor in gold-quartz veins. 

Main opaque minerals are chalcopyrite, pyrite, pyrrhotite, sphalerite and bornite (Table 2.22). These minerals commonly occur in massive, banded and disseminated ores and are usually metamorphosed. Hematite occurs in red chert which is composed of fine grained hematite and aluminosilicates (chlorite, stilpnomelane, amphibole, quartz) and carbonates. The massive sulfide ore bodies are overlain by a thin layer of red ferruginous rock in the Okuki (Watanabe et al., 1970). Minor opaque minerals are cobalt minerals (cobaltite, cobalt pentlandite, cobalt mackinawite, carrollite), tetrahedrite-tennantite, native gold, native silver, chalcocite, acanthite, hessite, silver-rich electrum, cubanite, valleriite , and mawsonite or stannoidite (Table 2.22). 

Tatsumi, T. (1952) Cubanite from cupriferous iron-sulfide deposits of the Makimine mine, Miyazaki Prefecture, Japan. Sci. Papers Coll. General Education, U. Tokyo, 2, 175-187. 

Anhydrite, CaSC>4 Barite (trace), BaSC>4 Cubanite (trace), CuFe2S3 Wurtzite (trace), ZnS Covellite (trace), CuS Marcasite (trace), FeS2 Unidentified silicates, aluminosilicates (traces)... 

Figure 6.25. (a) A projection of cubanite (CuFe2S3) showing S in P positions (large atoms) with Cu (dark small atoms) and Fe (light small atoms) in T sites. (b) A projection of one layer of S in P positions and Cu and Fe in T sites. 

Fig. 46. The structure of cubanite CuFe2S3. The cations occupying tetrahedron layers in (a,c) planes are indicated below...

Cubanite, CuS.Fe2S3, is a bronze-coloured mineral found 4 m Cuba, whence its name. Hardness 4, density 4 0 to 4 2.5... 

Between 45 and 90°C, the reaction of cubanite with acidic ferric sulfate solutions followed linear kinetics, indicating that the rate-controlling step was some reaction occurring on the surface of the cubanite. The dissolution rate increased with ferric ion concentration and decreased with increasing concentration of sulfuric acid and ferrous sulfate. The naturally slow reaction was accelerated with the addition of NaCl or HCl. The addition of salt in a dump leaching operation would be a relatively easy and cheap procedure to attain increased reaction rates. 

FIG, 17.15, Portionof the structure of cubanite (CuFejSs) showing slabs of the wurtzite structure with the tetrahedra pointing alternately up and down. 

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