Gold Bearing Minerals

All these methods use selective features, which are not directly connected with gold contents. 

Gold has many intensive lines in the breakdown spectrum. In gold containing quartz the characteristic Au lines appear after a relatively long delay, the strongest one at 312 nm (Fig. 8.20). Gold concentrations in certain types of ore are quite within the range of LIBS sensitivity. For example, quartz-sulfide 

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Selection of a flotation technique for gold preconcentration depends very much on the ore mineralogy, gangue composition and gold particle size. There is no universal method for flotation of the gold-bearing minerals, and the process is tailored to the ore characteristics. A specific reagent scheme and flowsheet are required for each ore. 

There are two other aspects that should be mentioned here that may directly affect the choice of the milling process. First, the uranium ore often contains other metals that have commercial value, like vanadium or niobium, for example, and their recovery may influence the process selected for uranium recuperation. Second, uranium itself may be a by-product of other processes like gold extraction, niobium, and tantalum production or phosphoric acid manufacture. Thus, recovery of low levels of uranium from phosphates, columbite, or gold-bearing minerals may not be economical in itself, but extracting uranium as a by-product from the waste streams of these operations could be commercially sensible. 

Arsenic is widely distributed about the earth and has a terrestrial abundance of approximately 5 g/t (4). Over 150 arsenic-bearing minerals are known (1). Table 2 fists the most common minerals. The most important commercial source of arsenic, however, is as a by-product from the treatment of copper, lead, cobalt, and gold ores. The quantity of arsenic usually associated with lead and copper ores may range from a trace to 2 —3%, whereas the gold ores found in Sweden contain 7—11% arsenic. Small quantities of elemental arsenic have been found in a number of localities. 

It is noteworthy that bornite, chalcocite and tetrahedrite-tennantite which are common minerals in Kuroko deposits occur in gold bearing Besshi-type deposits. Although these minerals are considered to be secondary minerals, depositional environments of these minerals are characterized by higher /s, and foj conditions. It is also noteworthy that these deposits are rich in pyrite rather than pyrrhotite. Probably, Besshi-subtype deposits in Shikoku formed under the higher fo and /sj conditions than the deposits characterized by pyrrhotite (Maizuru, Hidaka, Kii, east Sanbagawa). Such typical Besshi-type deposits (Besshi-subtype deposits in Shikoku) are characterized by simple sulfide mineral assemblage (chalcopyrite, pyrite, small amounts of sphalerite). Inclusion of bornite in pyrite is also common in these deposits. 

Flotation of gold-bearing sulphides from ores containing base metal sulphides present many challenges and should be viewed as flotation of the particular mineral that contains gold (i.e. pyrite, arsenopyrite, copper, etc.), because gold is usually associated with these minerals at micron size. 

The fossil placer deposits are in fact gold-bearing conglomerates that carry small amounts of PGM, together with gold, uranium and other heavy minerals. However, studies conducted revealed that some of the fossil placer deposits contain about 22 PGM species, including Ir-Os-Ru alloys, sperrylite and isoferroplatinum. 

The purpose of this paper is to describe the gold-bearing sulfide-carbonate-quartz veins of the MRG in order to compare this deposit with similar styles of gold mineralization is the region. 

The HMC deposit has four alteration mineral assemblages that grade from the background greenschist facies to quartz-albite-ankerite-sericite proximal to individual veins (Smith Kesler 1985). Studies of the HMC mine area have shown that higher concentrations of As, Ba, CO2, Rb, K2O, and As occur near gold-bearing zones (Whitehead et al. 1981). Specifically, either the C02/Ca0 molar ratio, or a combination of K2O and As concentrations can be used to discern mineralized from barren zones. 

Rhodium occurs associated with platinum ores, and also in the mineral rhodite in die gold-bearing sands of Brazil and Colombia. 

Arsenian pyrite is one of the more important host minerals for gold (Reich et al., 2005 Arehart, 1996). Gold probably exists as a solid solution (Au+) in arsenian pyrite or as Au(0) nanoscale inclusions within the minerals (Reich et al., 2005, 2781). Gold-bearing arsenian pyrite may form through the following reaction in hydrothermal fluids (Reich et al., 2005, 2790) ... 

The presence of carbonaceous material in the ore precipitates the gold in cyanide solutions, thus resulting in an increase of gold content in the cyanidation residue. For such complex gold-bearing ores, a roasting operation oxidizes the carbonaceous matter and thereby makes the ore more amenable to cyanidation. However, the alteration of the associated minerals presents new dissolution problems which must be solved. 

Stichbury M.-L., K., Bain J. G., Blowes D. W., and Gould W. D. (2000) Microbially-mediated reductive dissolution of arsenic bearing minerals in a gold mine tailings impoundment. Proc. 5th Int. Conf. Acid Rock Drainage 1, 97-103. 

Thorium is normally present in low concentrations in gold-bearing ores its presence is indicated by detectable concentrations of thoron daughters in return air in most gold mines that are, or were, uranium producers. In some areas thorium is present in elevated concentrations in a layer of black mineral sand above the gold bearing reef. Thorium or its decay products have also been detected in some radium bearing scales in acid plants. 

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