Calcite CaCO

Chemical Bond Formation (Chemisorption). This is the mechanism that leads to the formation of the strongest bonds between coUectors and mineral surfaces. Chemically adsorbed reagents usuaUy form surface compounds at the active waU sites. The flotation of calcite (CaCO ) and... 

The hydrogen ion flux that is provided by carbonic acid dissociation also can attack calcite (CaCO ) ... 

By this reaction, we can expect the modeled fluid to be rather acidic, since it is rich in potassium. We could have chosen to fix pH by equilibrium with the siderite, which also occurs in the veins. It is not clear, however, that the siderite was deposited during the same paragenetic stages as the fluorite. It is difficult on chemical grounds, furthermore, to reconcile coexistence of the calcium-rich ore fluid and siderite with the absence of calcite (CaCOs ) in the district. In any event, assuming equilibrium with kaolinite leads to a fluid rich in fluorine and, hence, to an attractive mechanism for forming fluorite ore. 

Solid solutions will only form between ions with similar radii ( 15 %). Table 3.15 shows the radii in crystal lattices of divalent cations that might form solid solutions in soils. Hence, for example Mn +,Fe + and Cd + might be expected to form solid solutions in CaCOs, but Cu + and Zn + would not. However, soils do not necessarily behave the same as pure systems. Thus there is little evidence for strong association of Cd + or Pb + with calcite (CaCOs) in soil systems, despite having similar radii to Ca + (McBride, 1994). However Cd + and Pb + are both commonly associated with hydroxyapatite (Caio(P04)6(OH)2),... 

Carbonates Aragonite CaCOs, calcite CaCOs, cerussite PbCOs, magnesite MgCOs, strontianite SrCOs, witherite BaCOs... 

The electrostatic valence rule usually is met rather well by polar compounds, even when considerable covalent bonding is present. For instance, in calcite (CaCO,) the C + ion has coordination number 6 and thus an electrostatic bond strength of 5 (Ca ) = j. For the C atom, taken as C + ion, it is s(C ) = j. We obtain the correct value of z for the oxygen atoms, considering them as ions, if every one of them is surrounded by one C and two Ca particles, z = -[25(Ca2+) + 5(C " )] = -[2 j - -1] = -2. This corresponds to the actual structure. NaNO, and YBO, have the same structure in these cases the rule also is fulfilled when the ions are taken to be Na+,, Y-+, and For the numerous silicates no or only marginal deviations result when the calculation is performed with metal ions, Si " and 0 ions. 

A similar rate phenomenon is used by mineralogists to distinguish calcite from dolomite. The smaller and more polarizing Mg+2 ions lower the polarizability of the (C03) 2 ions to such an extent that dolomite does not effervesce when brought in contact with dilute HC1. Calcite (CaCOs) reacts readily with the dilute acid. 

Inside the system, the acido-basic equilibria are always reached. Nevertheless, solutions can be supersaturated regarding the two mineral species, calcite (CaCOs) and calcium oxalate (CaC204). 

Fxcept for the difference in color, crystals of rhodochrosiie. MnCOg. and calcite, CaCO . resemble each othet very sto)iiglv fFig. 8 51 Ci ystals of ammomum sulfate, potassium sulfate, KoSOp aie also very similar to one another in... 

The most abundant carbonate minerals in mine wastes are calcite [CaCOs], dolomite [CaMg(C03)2], ankerite [Ca(Fe,Mg)(C03)2], siderite [FeC03] or mixtures thereof. The dissolution of calcite can be described as... 

Figure 1. Raman spectra of R5 and S5 catalysts (Ca/Pd=2.0) and the support (G-59) referred to calcite (CaCOs) and woUastonite (CaSiOs).

Some solids are only weakly soluble in water but dissolve readily in acidic solutions. Copper and nickel sulfides from ores, for example, can be brought into solution with strong acids, a fact that aids greatly in the separation and recovery of these valuable metals in their elemental forms. The effect of pH on solubility is shown dramatically in the damage done to buildings and monuments by acid precipitation (Fig. 16.8). Both marble and limestone are made up of small crystals of calcite (CaCOs), which dissolves to only a limited extent in natural rain (with a pH of about 5.6) but dissolves much more extensively as the rainwater becomes more acidic. The reaction... 

The regional distribution of hardness (i.e. Ca plus Mg) is shown in Fig. 4. This probably reflects the distribution of free carbonates in the sediments with areas of hard water reflecting their presence and low hardness areas reflecting their absence. The most probable carbonate minerals are calcite (CaCOs) and dolomite (CaMg(C03)2). The absence of pH and bicarbonate data from the National Hydrochemical Survey dataset means that saturation indices for these minerals could not be calculated. However, data from the three Special Study Areas (Smedley et al., 2001) suggest that there is both calcite and dolomite saturation, even slight supersaturation. 

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