Pyrite fine-grained

The vein is composed of rhythmic banding of quartz layers and fine-grained sulfides such as argentite, acanthite, sphalerite, galena, pyrite and chalcopyrite, and elec-trum. The principal gangue minerals are quartz, calcite, adularia and interstratified chlorite/smectite. Minor minerals are inesite, johansenite, xonotlite and sericite. These gangue minerals except for quartz, adularia, calcite and sericite are not found in the wall rocks. 

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). 

Fig. 2. SEM backscattered electron image of a Type II vein containing euhedral to cataclastically brecciated arsenopyrite (asp), pyrite (py), quartz, and calcite. A thin Type 1 quartz vein showed a SEM-EDAX analysis of a very fine-grained mineral mass rich in Hg-Au-As vein (arrow).

Five different vein phases (Types i to V) are recognized at both deposits, aii have variabie amounts of carbonates and quartz gangue. Type i veins contain oniy brecciated quartz and carbonate minerals and at ED are spatially associated with disseminated arsenopyrite, chalcopyrite, pyrrhotite, and pyrite in the mafic host rock. Type II veins in both deposits are partly brecciated and contain 5-80% sulfides of dominantly pyrite, arsenopyrite, and at GB chalcopyrite. Type III veins are quartz-calcite-tetrahedrite-bismuthinite microveins that cut both Types I and II veins. The fine-grained sulfides replace and enclose arsenopyrite and pyrite in Type II veins and are also visible in microfractures within the Type II sulfides. Type IV veins are base-metal rich and characterized by galena, sphalerite, chalcopyrite, pyrite, and stibnite with a maximum width of 20 cm. The Type V veins are late barren-carbonate veins cutting all previous veins and textural features. 

The nodules are found in gray-black commercial slate having fine grain size, uniform color and texture, and well developed slaty cleavage. Such slate occurs in thick strata marked only by thin black bands ( ribbons ) of somewhat coarser texture, and by rare, disseminated knots, siliceous nodules of foreign material. The slate is a mixture of quartz, illite, chlorite, caldte, and muscovite, with minor amounts of pyrite, carbonaceous matter, and heavy mineral grains. The dark color is attributed to finely disseminated carbon and pyrite. An analysis of the slate is given in Table I. 

Shales are very fine-grained sedimentary rocks consisting of 67 % or more clay-sized (<4 pm) particles. Unlike mudstones, siltstones, and claystones, shales are very laminar and fissile that is, they readily split into thin, closely spaced, and parallel layers (Boggs, 1995), 181. Along with clay minerals, shales may have abundant microscopic quartz, feldspars, pyrite, hematite, calcite, dolomite, and/or organic matter (Boggs, 1995), 178. 

Figure 5 Summary of iron speciation in fine-grained siliciclastic sediments and sedimentary rocks. Total Fe (Fct) is equal to the sum of all these fractions. DOP increases in oxic sediments through the conversion of Fcex to Fcpy, although the HCl procedure generally overestimates the readily reactive iron available. In euxinic settings, high DOP values (Fcx/Al ratios) result from scavenging of dissolved iron during pyrite formation in the water column. See Section 7.06.3.4.3 and Lyons et aL (2003) for further discussion and background.

A similar relationship between Hg and target elements has been defined at the Lady Loretta deposit, also in northern Queensland (Loudon et al., 1975 Carr, 1981, 1984). Here the ore body consists of a stratiform lens, up to 40 m thick, hosted within fine-grained sedimentary rocks occurring in a steep-sided basinal structure. The ore outcrops on the western limb of this structure however, to the east, Zn and Pb sulphides pinch out rapidly, giving way to massive pyrite with interbedded dark, fine silt-shales. The ore-bearing rocks and their pyritic equivalents stand out as ridges, remnants of a... 

Of basic importance when determining risk is the absolute and relative amounts of the exposed pyrite that occur above or below the water table. Above the water table, oxidation rates are usually catalyzed by bacteria and can be very fast in fine-grained waste-rock piles. Rates in water-saturated spoil materials or below the water table are generally much slower because of the unavailability of free oxygen. 

This classification is useful in that the removal of minerals from coal in preparation plants is strongly influenced by the mineral s physical mode of occurrence. Fine-grained quartz, clay, and pyrite disseminated within macerals are least susceptible to removal by physical cleaning methods whereas rock fragments and minerals in layered, nodular, and fissure modes break free and are more easily removed. 

Voltzia sandstones 20 m thick fine-grained, micaceous and feldspathic sandstones, often containing pyrite. 

Fine-grained pyrrhotite + pyrite + sphaierite intergrowths in an anhydrite matrix... 

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