Limestone dolomitic

Chemical-grade limestone is a pure type of high calcium or dolomitic limestone used by the chemical-process industry or where exacting chemical requirements ate necessary. It contains a minimum of 95% total carbonate. In a few areas of the United States this minimum may be extended to 97 or 98%. 

Dolomitic limestone contains considerable MgCO. A tme dolomitic stone contains a ratio of 40—44% MgCO to 54—58% CaCO. However, the term is mote loosely used to denote any carbonate rock that contains mote than 20% MgCO. It varies in color, hardness, and purity. 

Marble is a metamorphic, highly crystalline rock that may be high calcium or dolomitic limestone of varying purity. It occurs in virtually every color in diverse motded effects and is the most beautiful form of limestone. It is usually very hard and can be cut and poHshed to a very smooth surface. 

Whiting at one time coimoted only a very fine form of chalk of micrometer sizes but the term is now used more broadly to include all finely divided, meticulously milled carbonates derived from high calcium or dolomitic limestone, marble, shell, or chemically precipitated calcium carbonate. Unlike all of the above natural forms of limestone, it is strictly a manufactured product. 

Many lime plants are able to reduce the impurities in their lime product by careful screening and selecting of stone for burning. Because 9 kg of limestone produce only 5 kg of quicklime, the percentage of impurities in a quicklime is nearly double that in the original stone. Analyses of typical samples of high calcium, magnesian, and dolomitic limestones found in the United States are Hsted in Table 1. 

Hardness. Most limestone is soft enough to be readily scratched with a knife. Pure calcite is standardized on Mohs scale at 3 aragonite is harder, 3.5—4. Dolomitic limestone is generally harder than high calcium. Dead-burned or sintered limes are 3—4 on this scale, whereas most commercial soft-burned quicklimes are 2—3 (see Hardness). 

Thermal Properties. Because all limestone is converted to an oxide before fusion or melting occurs, the only melting point appHcable is that of quicklime. These values are 2570°C for CaO and 2800°C for MgO. Boiling point values for CaO are 2850°C and for MgO 3600°C. The mean specific heats for limestones and limes gradually ascend as temperatures increase from 0 to 1000°C. The ranges are as follows high calcium limestone, 0.19—0.26 dolomitic quicklime, 0.19—0.294 dolomitic limestone, 0.206—0.264 magnesium oxide, 0.199—0.303 and calcium oxide, 0.175—0.286. 

Stability. AH calcitic and dolomitic limestones are extremely stable compounds, decomposing only in fairly concentrated strong acids or at calcining temperatures of 898°C for high calcium and about 725°C for dolomitic stones at 101.3 kPa (1 atm). A very mild destabilizing effect is caused by C02-saturated water, as described in the preceding section on solubihty. Aragonite, however, is not as stable as calcite. In sustained contact with moisture,... 

The neutralising power of lime and limestone and other alkaUes is compared in Table 2 (8). Of all these alkaUes, MgO is the strongest base, followed by CaO. Thus neutralization of a given acid requires less dolomitic limestone or lime than high calcium limestone or lime. 

Drilled solids include active drilled solids and inactive drilled solids. Clays and shales are considered to be active drilled solids they disperse into colloidal size readily and become detrimental to drilling by increasing the apparent viscosity and gel strength of the mud. Inactive drilled solids are sand, dolomite, limestone, etc. if they occur in colloidal size, these solids may increase plastic viscosity of the drilling mud. 

A high neutron porosity and low density porosity occur in the shale zones 2256-2274 and 2356-2388 ft. In the clean zone, around 2280-2290 ft, the cleanest part reads = 18% and = 13%. Plotting the point in the CNL chart of Figure 4-303, the rock matrix appears to be a dolomitized limestone and the true porosity is 17%. 

In general, the calceous-dolomitic rocks from the Cambrian age are affected by their upper beds, by sulphide mineralization of lead, zinc and iron contemporaneous with sedimentation. The oxide lead and zinc minerals are disseminated through dolomitic limestone. As a consequence of the action of the descending process, these formations may assume different types of mineralization. According to the intensity of the oxidation process, which is associated with the different characteristics of the country rock, this country rock may be (a) principally calceous, (b) calceous with dolomitized zones and (c) primarily dolomitized. 

Table 8.8 Compositions of superficial and deep waters of the Sarcidano region (Sardinia, Italy) equilibriated with Mesozoic dolomite limestones (Bertorino et ah, 1981). Values in mEq/1. C-j- total inorganic carbon in mmol/1.

The alkali sulphites and bisulphites are produced on the large scale by treating lime and magnesia or dolomitic limestone with sulphur dioxide in the presence of water, then adding the requisite amount of alkali sulphate to the filtrate and filtering off any insoluble sulphate 3 or, alkali carbonate or bicarbonate may be treated directly with sulphur dioxide.4... 

ANTHRAXOL1TE. A coal-like metamorphosed bitumen, often closely associated with igneous rocks. Commonly associated with Herkimer Diamond type quartz crystals in dolomitic limestones in Herkimer and Montgomery counties in New York State. 

I. Cahoon (19S4) hydrothermal alteration of dolomitic limestone, Milford, Utah, U.S.A. analyst W. Savournin. 

Chukhrov et al. (1963) colorless glassy incrustations on dolomitized limestone, Podolsk district near Moscow analyst V.A. Moleva. 

Figure 8.24. Summary of composition of nonstoichiometric dolomite. A. Data for 246 samples from continental exposures of dolostones and dolomitic limestones. B. Data for 153 samples from continental exposures of dolomites related and not related to evaporite sequences. C. Ranges of Holocene dolomite compositions. D. Data for 35 samples of deep-marine dolomite from DSDP cores. E. Histogram of 245 samples of deep-marine dolomite E evaporite-associated, O organic origin, L samples of Lumsden (1988) above, D detrital, and U uncertain. (After Lumsden, 1988.)...

Magnesium hydroxide is produced by precipitation of the magnesium ions with Ca(OH)2 obtained from dolomitic limestone. The limestone is calcined in a rotary kiln to produce lime the lime is reacted with water to give Ca(OH)2, which reacts with the Mg ions in the brine to give Mg(OH)2. One-half of the Mg(OH)2 comes from the dolomitic lime. The slurry of Mg(OH)2 in the CaCl2 brine is thickened in settling tanks and filtered, and the CaCl2 is washed out of the cake with water. 

Lime (a) from crushed limestone, (b) from oyster or sea shell, and (c) from dolomitic limestone... 

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