Pyrite and calcite

Once the pure mineral powders characterized, 3 mixtures were manually prepared and named ML1, ML2 and ML3. They contain each of the 8 minerals in different proportions reproducing 3 mine tailings falling in the uncertainty zone of the static test used. The 3 synthetic tailings were characterized with the same techniques as for the pure minerals. Cp and Sp weight fractions were evaluated from their chemical element tracers (respectively Cu and Zn) obtained from ICP-AES analysis. Qz, Dol, and Sid samples are considered pure and their percentages in the mixtures are not corrected. Table 1 presents the fraction of each mineral in the three mixtures before and after correction taking into consideration the contamination of Po sample by pyrite and calcite, as previously determined. The corrected mineral proportions are used for calculation of the static test parameters based on... 

KINETICS needs three subdivisions for organic matter, pyrite and calcite, respectively. It is not relevant, in which block the time steps are defined. Using -step divide 1000000 , the step width is cut down at the beginning of the kinetic calculations according to the quotient total time/step divide. 

Other less common elements recorded in these analyses are tin, chromium, and nickel. The tin is found among some of the opaque constituents (minerals) and is thought to be present as the mineral cas-siterite (Sn02), which is reportedly (17) associated with sulfide mineralization. Less is known about the location of the chromium, which may be a minor element in more than one mineral, e.g., pyrite and calcite. Nickel, on the other hand, is associated with sulfur, as can be shown in the X-ray spectra (Figure 10) obtained from a diamond-shaped mineral fragment. The analysis was obtained in the reflection (SEM) mode on the STEM, which excluded the recording of an electron diffraction pattern. The mineral tentatively is identified as millerite, a nickel sulfide (NiS) with no iron and a 1 1 ratio of nickel to sulfur. However, these conclusions must be considered as tentative until positive identification of the nickel sulfide is possible. 

Because the most reactive phases found in the experiments with pairs of minerals were clays, calcite, and pyrite, these were prepared in triplet mounts. In trials using either montmorillonite or illite with calcite and pyrite, a liquid formed at the mutual boundary of the latter pair at 600-650°C. Pyrite and calcite had, of course, previously reacted and this liquid therefore occurred between the product phases pyrrhotite and lime. Subsequent x-ray analysis showed the presence of pyrrhotite, lime, and oldhamite. In both instances, the temperature of this reaction was lower than that obtained in the pair mount of calcite and pyrite, 1140 C. When kaolinite was in the mount with calcite and pyrite, the same reaction occurred at 750-760 C. Though the mechanism by which the clays reduce the reaction temperature is not yet understood, the differences in reaction temperature with and without clay is considered significant. 

The main chemical composition of an aquifer is deep anoxic, mainly quartz sand, poor in organic carbon, containing a small amount of pyrite and calcite. Cation-exchange capacity (CEC) is low, dominated by Ca and Mg. The top of the layer contains more organic carbon, calcite, and pyrite. 

An aggregate of lazurite with variable amounts of pyrite and calcite... 

If pyrite and calcite form during diagenesis according to reaction (5.61), O2 generates. However decompositions of pyrite and calcite by weathering cause lower atmospheric O2 concentration. Above reaction implies that atmospheric O2 concentration depends not only on O2 cycle but also on S, Ca and Fe cycles. Sr incorporates into carbonate. Therefore, O2 concentration also depends on Sr cycle. 

Slates are related to clays. The DTA technique has been applied to study the weathering quality as well as an aid to the identification of slate of unknown origin. Figure 17 shows the differential thermal analysis of samples of roofing slate of three different qualities.The first curve represents a slate of excellent durability. The peaks at 610 and 850°C may be due to some type of chlorite. The inflection at 575 C is caused by the presence of quartz. In the calcined material (2 curve), the presence of quartz is more clear. The third curve is obtained with a slate that was found in practice to delaminate slowly on roofs under conditions of low atmospheric pollution. The poor durability may be caused by the slow oxidation of pyrite in the slate and subsequent reaction between the oxidation product and calcite to form calcium sulfate. The presence of pyrite and calcite is indicated by the peaks at 450° and 770°C, respectively. The fourth curve of slate of pure quality is dominated by the large calcite peak. The exothermic peaks at 930° and 420°C suggest the presence of chlorite and a small amount of pyrite, respectively. 

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