Classification of Limestones

Limestone takes many forms. The following eleven descriptions include the great 

Most classifications have been developed by and for geologists. However, when selecting a limestone deposit for quarrying, the developer is concerned with its physical and chemical properties and their influence on the suitability of the products for the intended end-uses. Similarly, a lime producer would be interested in the characteristics of the limestone fed to the kilns, how it responds to heating, and the physical and chemical properties of the resulting lime products. These aspects are considered in greater detail in later chapters. 

Many ways of classifying limestone have been developed to describe the nature of the deposit. Six of these are described briefly below  

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The grain size of the limestone formed the basis of early classifications of limestone lithic type the same approach was used for dolostones but with different modifying terms. Since the 1950 s combined genetic and descriptive limestone classifications have developed, based principally on the recognition that a carbonate sediment contains three major components (1) a framework of discrete grains or... 

Folk R.L. (1959) Practical petrographic classification of limestones. AAPG Bull. 43, 1-38. 

Figure 5.4. Classification of mixed siliciclastic-carbonate sediments proposed by Mount (1985). It is an unfolded tetrahedron in which the apices are siliciclastic sand, carbonate allochems, siliciclastic mud, and carbonate micrite. For comparison with Folk s (1962) classification, the classification of pure fossiliferous limestone is also plotted.

In an exploration area in northern Peru, igneous rocks cover an area of several square km within a metamorphosed series of quartzites and limestones. The younger sequence consists of ignimbrites, tuffs and tuffites of approximately 1000 m thickness. The metamorphism produced skams, which are connected with the ore body. A porphyry Cu deposit occurs in the metamorphosed rocks and is characterised by intense hydrothermal alteration (quartz-kaolinite-sericite) which makes determination and classification of magmatic and sedimentary rocks at the surface very difficult. A zone of propylitic alteration can locally be followed up to 500 m into the andesitic-dioritic wall rocks. 

Keith, M.L. Weber, J.N. (1964) Isotopic composition and environmental classification of selected limestones and fossils. Geochim. Cosmochim. Acta, 28,1787-1816. 

Fly ash starts out as impurities in coal, mostly clay, shales, limestone, and dolomite, which ends up as ash, and fuse at high temperature becoming glass. Two U.S. classifications of fly ash are produced. Class C and Class F, according to the type of coal used. Class C fly ash, typically obtained from subbituminous and lignite coals, must have more than 50% total of silica, alumina, and iron oxide. Class F fly ash, typically obtained from bituminous and anthracite coals, has more than 70% of these oxides. 

Mass transfer with chemical reaction in multiphase systems" covers, indeed, a large area. Table 1 shows a general classification of the systems encountered. From the possible two-phase systems, solid-solid reactions, liquid-solid (reactive or catalytic) and gas-solid (reactive or catalytic) reactions are not discussed here. The first one was reviewed by Tamhankar and Doraiswamy (2) and gas-solid (reactive) systems, such as, coal gasification, calcination of limestone, reduction of ores, etc. have been treated in some detail in recent reviews (3-5). The industrially important fluid-solid catalytic processes were the topic of a previous Advanced Study Institute (6) and have been also discussed authoritatively elsewhere (5,7). Concerning solid (reactive)-liquid two-phase systems, only some interesting examples are presented in Table 2 (1). 

Tintinnina are marine and freshwater ciliate protozoans, which secrete an organic cupshaped test termed a lorica. The lorica may be covered by agglutinated mineral grains, and the shape and manner of construction of the lorica are the basis of classification of the group. Fossil tintinnids are abundant in some fine-grained limestones of Mesozoic age, but these are... 

Whereas Geldart s classification relates fluidized-bed behavior to the average particle size in a bed, particle feed sizes maybe quite different. For example, in fluidized-bed coal (qv) combustion, large coal particles are fed to a bed made up mostly of smaller limestone particles (see Coal conversion processes). 

Agricola divides the minerals into 1. earths, such as clays, chalks, ochres, etc. 2. stones, properly so called, gems, semiprecious stones. 3. solidified juices, (succi concreti), salt, alum, vitriols, saltpeter, etc. This is an application of the theory of the ancients that these are derived from solidified waters. 4. rocks, such as marble, serpentine, alabaster, limestone, etc., hard and not friable like the earths. 5. metals. 6. compounds, or mixtures, under which head he classes various ores of the metals, from which he recognizes that simpler constituents, as the metals, may be obtained. The fundamental basis of this classification Agricola explains in the following manner.80... 

Both classifications are based on the depositional texture of the limestone Folk s emphasis is on the similarity of carbonate sedimentation to that of sandstones, resulting in a scheme employing as variables the lime mud spar cement ratio and allochem composition. Allochems may be intraclasts, ooids, fossils or... 

Limestone, Ground, is produced as a fine, white to off white, microcrystalline powder mainly consisting of calcium carbonate. It is obtained by crushing, grinding, and classifying naturally occurring limestone benefited by flotation and/or air classification. It is stable in air. It is practically insoluble in water and in alcohol. The presence of any ammonium salt or carbon dioxide increases its solubility in water, but the presence of any alkali hydroxide reduces its solubility. 

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