China
Africa
Explore chapters and articles related to this topic
Chemistry of Acid Mine Drainage Formation
Published in Geoffrey S. Simate, Sehliselo Ndlovu, Acid Mine Drainage, 2021
The process of pyrite oxidation relates to all sulphide minerals once exposed to oxidizing conditions (e.g., chalcopyrite, bornite, molybdenite, arsenopyrite, enargite, galena and sphalerite among others). In other words, while the principal sulphide mineral in mine wastes is pyrite, other sulphide minerals are also susceptible to oxidation releasing elements such as aluminium, arsenic, cadmium, cobalt, copper, mercury, nickel, lead, and zinc into the water flowing through the mine waste (Blowes et al., 2003). The oxidation of other sulphide minerals is discussed in the next sections.
The gold metallotect in the Eastern Desert of Egypt
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
At Wadi Hammad, supergene alteration of the highly fractured and deeply weathered porphyritic andesite, which hosts sulfides at the contact with a porphyritic granite body, resulted in the remobilization and precipitation of secondary minerals including supergene gold. Gold was remobilized through several processes involving sulfidization, carbonatization and oxidation. Petrographic investigations and microprobe analyses revealed four main types of gold; the first is very fine native gold blebs (5µm) with appreciable As-contents reaching 1.27 wt% and a very high Ag-content up to 44.57 wt%, found as inclusions inside galena. It is associated with sphalerite, chalcopyrite, bornite, and enargite. The temperature gradient of this paragenesis as revealed from chalcopyrite disease is 200-300 °C. The second type is in the form of elongated gold spikes (20-50 µm long) inside fissured quartz, it shows remarkable Ag-contents and grades into electrum (21-38 wt % Ag). The third gold type is supergene botryoidal gold (50-250 µm), found in the outer and inner parts of the low-temperature collomorphic chalcocite, filling microfractures in the tuffites and quartz. It shows golden yellow colors of reflectivity, collomorphic texture, and is Ag-poor. Another form of supergene gold (20-80 µm) is found along the contact between chalcocite and goethite and inside the malachite cement, it reveals remarkable Ag and Cu admixtures, whereas the As-content is negligible. The fourth gold type is found inside the highly weathered collomorphic goethite and hydrogoethite. It is a very pure variety of gold (up to 98.59 wt % Au) and is considered as residual gold, which remained behind after extensive oxidation of the gold-bearing sulfides. The supergene and residual gold grains are rounded, they show re-grown boundaries and coagulate around larger gold grains.
Leaching with Ferric and Cupric Ions
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2019
The reported studies on ferric sulfate leaching of various copper sulfide minerals include covellite, chalcocite, chalcopyrite, bornite, cubanite, enargite, and tetrahedrite-tennantite. Salient features of these investigations are presented below.
The Synergistic Copper Process concept
Published in Mineral Processing and Extractive Metallurgy, 2018
William Hawker, James Vaughan, Evgueni Jak, Peter C. Hayes
Copper is found in a range of different minerals, for example, copper and mixed metal sulphides, oxides, carbonates and hydroxides. The deposit types, and the resulting minerals and mineral associations, reflect the different geological processes by which these deposits are formed. In general, these minerals are grouped into sulphide-based and oxide-based deposits. The majority of the primary copper resources currently available are in the form of sulphide minerals (Mudd et al. 2013), for example, chalcopyrite, CuFeS2; chalcocite, CuS; bornite, Cu5FeS4; enargite, Cu3AsS4. Most oxide-based deposits, containing minerals, such as tenorite, CuO; chrysocolla, Cu2H2Si2O5.nH2O azurite, Cu3(CO3)2(OH)2; malachite, Cu2CO3(OH)2; have been formed as a result of exposure of the original sulphide minerals to atmospheric oxygen (Guilbert and Park 2007). As a result, oxide deposits are commonly found to be associated with major sulphide ores, and are generally smaller in size and in the form of surface outcrops.
Alteration and mineral zonation at the Mt Lyell copper–gold deposit, Tasmania
Published in Australian Journal of Earth Sciences, 2018
The high-grade ore occurs as pods in, or adjacent to the Great Lyell Fault, and on the major 060°-trending fault at the southern end of the orebody. The high-grade ore is commonly associated with massive hematite, barite and ‘chert’ (Figure 9). The association of high-grade Cu–Ag ore with intensely silicified volcanics (cryptocrystalline silica) and massive hematite–barite and barite is similar to that observed at North Lyell (e.g. Corbett, 2001a, 2001b). The high-grade ore is dominantly chalcopyrite, bornite, chalcocite with locally abundant stromeyerite and accessory tetrahedrite–tennantite, mawsonite, enargite, galena, sphalerite, stannoidite, arsenopyrite and molybdenite. Grades of +20 wt% Cu and +3 wt% Ag were common. The massive pyrite (away from the Great Lyell Fault contact) is dominantly pyrite with only low levels of Cu in tennantite–tetrahedrite and chalcopyrite. Old production records indicate the massive pyrite, which was the majority of the deposit, assayed about 0.4 wt% Cu, 0.4–3.0 g/t Au and 30–100 g/t Ag. Total production for the Iron Blow orebody was 5 586 000 tonnes @ 1.29 wt% Cu, 1.99 g/t Au and 61.22 g/t Ag (Reid, 1976).
Alkaline sulphide leaching of tennantite in copper flotation concentrates to selectively dissolve arsenic
Published in Mineral Processing and Extractive Metallurgy, 2021
Jacqueline Cuevas, Warren John Bruckard, Mark Ian Pownceby, Graham Jeffrey Sparrow, Aaron Torpy
Filippou et al. (2007) proposed that for alkaline sulphide leaching of arsenic and antimony from copper minerals, the copper product is chalcocite (Cu2S), or covellite (CuS), depending on the copper minerals in the leach feed. The arsenic and antimony are dissolved as thioanions (e.g. thioarsenate () and thioantimonite ()). Simplified equations for the dissolution of arsenic from enargite and tetrahedrite with sodium sulphide are shown in Equations (4–6).