Mica schist

Muscovite mica formed as a primary mineral in pegmatites and granodiorite differs in physical properties compared to muscovite mica formed by secondary alteration (mica schist) (Table 2). The main differences are in flexibiUty and abiUty to be delaminated. Primary muscovite is not as brittle and delaminates much easier than muscovite formed as a secondary mineral. Mineralogical properties of the principal natural micas are shown in Table 3. The make-up of muscovite, phlogopite, and biotite are as follows ... 

Mica schist deposits range in consistency from loosely consoHdated soil to fairly hard ore and vary in color from brown to almost white. These ore bodies are noted for thek micaceous appearance, which results from a 40—90% mica content. Mica sizes vary from <44 fim to - 1.5 cm. 

Flake mica is also produced from mica schist which normally contains from 30—60% recrysta11i2ed muscovite mica along with quart2 and iron minerals. The quart2 is usually not suitable for glass sand or high purity material, however. 

Graphite is widely distributed throughout the world though much of it is of little economic importance. Large crystals or flake occur in metamorphosed sedimentary silicate rocks such as quartz, mica schists and gneisses crystal size varies from <1 mm up to about 6 mm (average 4mm) and the deposits form lenses up to 30 m thick stretching several... 

Beryl is found in granite rocks and especially in pegmatites, but it occurs also in mica schists in the Urals. In addition to the many European localities, including Austria, Germany, and Ireland, beryls of... 

Masterson 58-52-22-3 podzolic Tehama Co., Calif., U.S.A. mica, schist 5.3 alteration of mica... 

Dolomites Quartzites Conglomerates Quartz- amphibole-mag-netite quartz-mica schists... 

Table 3 lists examples of more than a dozen different chemical types of river water. Although Ca and HCO j" are generally dominant, Mg dominance over Ca + can be found in rivers draining various lithologies such as basalt, peridotite, serpentinite, dolomite, coal, or where hydro-thermal influence is important (Semliki). Sodium may dominate in sandstone basins, in black shales (Powder, Redwater in Montana), in evaporitic sedimentary basins (Salt), in evaporated basins (Saoura), and where hydrothermal and volcanic influence is important (Semliki, Tokaanu). rarely exceeds 4% of cations, except in some clayey sands, mica schists, and trachyandesite it exceeds 15% in extremely dilute waters of Central Amazonia and in highly mineralized waters of rift lake outlets (Semliki, Ruzizi). 

Tirrawarra Sandstones in the Moorari and Fly Lake Fields consist mainly of medium-grained, moderately sorted sublitharenites (mostly mica schist and phyllite, shale and siltstone clasts) (classification of Folk, 1974). A variety of authigenic minerals are recognized, including syntaxial quartz overgrowths, minor illite, patchy kaolinite and siderite. Attention is focused on the siderite and only a short description of the other diagenetic minerals is provided here. 

Thompson JB Jr (1991) Modal space Applications to ultramafic and mafic rocks. Can Mineral 29 615-632 Thompson JB Jr (2000) Modal spaces for some peraluminous quartzo-feldspathic rocks and mica schists. Petrology 8 303-310 (Enghsh edn). Also printed in Petrologiya 8 339-346 (Russian edn, but this paper is in English). Note Fig. 1 on p 305 of the Petrology version is incorrect The corrected Fig. 1 is on p 341 of the Petrologiya version.)... 

Metamorphic rocks were formed by a secondary conversion of igneous and sedimented rocks, due to certain geological tectonic processes. The pressure, temperature, and chemical effects, particularly effects of gases and thermal solutions were the main factors in these conversions. The texture of metamorphic rocks may be characterized by the presence of layers or scales. Typical metamorphic rocks are gneisses, mica-schists, serpentines, crystalline limestones and crystalline dolomites. 

At Su Suergin, in Sardinia, the deposits occur at the contact of the Rhsctic limestone with Permian slate. Antimony glance, accompanied by pyrites, is also found in the mica schist. Traverse gave the opinion that these deposits are of sedimmtary origin rather than of vein formation. (E.)... 

Case study 4 for typical background values shale-type Al-rich silicate rocks (mica schists) from the Malcantone Area (Astano, Ticino/Switzerland)... 

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