Mineral composition sedimentary rocks

The mineral types familiar in sediments and sedimentary rocks are present micas, mica-like phases, fully expandable phases and mixed layered series. In a sense, celadonite mica is isolated from dioctahedral mica by a multiphase zone where montmorillonite is stable with a feldspar and mica. It is evident that the only way to. produce celadonite mica under high potassium concentrations is by having a proper bulk composition toward that of celadonite. The possibility of producing celadonite in a potassium deficient system, i.e., where montmorillonite coexists with a non-alkali bearing phase, has not yet been studied experimentally. 

Considering the compositions of the mixed layered minerals found in sedimentary rocks (Figure 25) it is obvious that magnesian-iron expandable dioctahedral minerals will be in equilibrium not uniquely with kaolinite but also in many instances with a magnesian-iron phase—either chlorite or an expanding trioctahedral mineral. In such a situation the slope in... 

Microprobe analyses of some berthierine pellets from sedimentary rocks (Velde, e t al., 1974, and new data, Figure 30) indicate that these minerals have compositions close to those of 7 8 chlorites delimited by synthesis studies and here there is a more restricted range of silica substitution in the structure than is found in 14 8 chlorites. Thus the two polymorphs have at least different limits in tetrahedral substitutions. 

Most commonly, zeolites are found in series of sedimentary rocks which contain pyroclastic material and are formed during the devitrification of this material. If the rocks are silica-rich, the zeolite species formed seems dependent upon the bulk composition and burial depth or temperature of formation (Hay, 1966). They are most frequently accompanied by silica in an amorphous or cryptocrystalline form (opal, chalcedony). Analcite and all other compositional intermediates up to the silica-rich clinoptilolite are found in this association. The most comifton clay mineral in such tuffs is montmorillonite. Zeolites are sometimes found with glauconite (Brown, et al . 1969) or celadonite (Hay, 1966 Iijima, 1970 Read and Eisenbacher, 1974) in pelitic layers or acidic eruptive rocks... 

Plagioclase A sodium and calcium aluminum silicate mineral that commonly forms in igneous and metamorphic rocks, and occasionally survives weathering to occur in sediments, soils, and sedimentary rocks. A solid solution exists in plagioclase, where (CaAl)5+ and (NaSi)5+ may substitute for each other to produce a composition that ranges from NaAISisOg to CaAUSiiOg. 

Sandstone a sedimentary rock formed by compaction and cementation of sand grains can be classified according to the mineral composition of the sand and cement. 

Sedimentary rocks form from particles eroded from older rocks, by precipitation from solution, or by organic activity. Sedimentary rocks are described by their mineral composition, grain size, texture, and origin (Table 2.12). 

Sedimentary rocks are typically a result of erosion and the interaction of the environment on igneous and metamorphic rocks they are formed by the aggregation of mineral particles or sediments. Their SiCVCaO percent composition can be quite varied for example, from 74.3/4.9 (sandstones) down to 8.2/40.5 (limestones). On the average, sedimentary... 

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