Silicates muscovite

Aluminum (Cent.) potassium silicate (muscovite) SAljOs-KjO-eSiOj- 796.40 mn., 1.590 2.9... 

Sheet silicates (muscovite, biotite and chlorite) are absent or occur only in minor amounts in most of the samples from the Upper Marine Molasse, whereas in the Lower Freshwater Molasse they can be locally more abundant. Minor or trace amounts of opaque and accessory minerals occur in each sample. In the Lower Freshwater Molasse the accessories are mostly heavy minerals, whereas in the Upper Marine Molasse they are typically glauconite grains. 

Sheet silicates Muscovite Mica and kaolinite refer to ... 

CAS 12001-26-2 EINECS/ELINCS 310-127-6 Synonyms Cl 77019 Mica silicate Muscovite mica Phlogopite Sericite Suzorite mica... 

Silicates with layer. structures include some of the most familiar and important minerals known to man, partieularly the clay minerals [such as kaolinite (china clay), montmorillonite (bentonite, fuller s earth), and vermiculite], the micas (e.g. muscovite, phlogopite, and biotite), and others such as chrysotile (white asbestos). 

Fig. 14. Compensation plot for dehydroxylation of kaolinite ( ) and other layer-type silicates (X = montmorillonite, illite and muscovite) data and sources given in Table 11. (Redrawn, with permission, from Advances in Catalysis, ref. 36).

Dominant gangue minerals are quartz, muscovite, chlorite, actinolite, hornblende, epidote, and biotite (Table 2.22). Minor minerals are rutile, illite, sphene, and glauco-phane. It is interesting to note that silicate minerals such as chlorite, epidote, pumpellyite, and albite are common and actinolite has been reported from the basalt near the Ainai Kuroko deposits (Shikazono et al., 1995) and they are also common in the basic schist which host the Motoyama Kuno deposits (Yui, 1983). 

Table 10.2 Upper concentration limits for Henry s law behavior in silicates and oxides. Abbreviations Ab = albite Sa = sanidine PI = plagioclase Pel = alkaline feldspar Rb-fel = Rb-feldspar Ne = nepheline Mu = muscovite 01 = olivine Di = diopside Cpx = clinopyroxene Oxp = orthyporoxene Amph = amphibole Par = pargasite Gr = garnet Ilm = ilmenite ...

Silicate minerals that usually occur as spherulitic aggregates of fibers have formed as a result of the alteration of the many minerals subsumed within the category of biopyriboles. Alteration of the micas under hydrothermal conditions produces compositional variants on recrystallization such as hydrous muscovite. Some of these samples have been labeled asbestiform, probably because they are found in veins that criss-cross rock masses. Fibrous micaceous minerals also occur as discrete disseminated particles, although few detailed analyses of crystallites from the disperse occurrences have been made. Fibrous mica found in veins usually grades (composition-ally) into members of the serpentine mineral group, the clays or the chlorites. 

Synonyms Mica is a nonfibrous silicate occurring in plate form and includes nine different species muscovite is a hydrated aluminum potassium silicate also called white mica phlo-gopite is an aluminum potassium magnesium silicate also called amber mica other forms are biotite, lepidolite, zinnwaldite, and roscoelite... 

Figure 1.46 The structure of muscovite (mica), a sheet silicate. Reprinted, by permission, from L. G. Berry, B. Mason, and R. V. Dietrich, Mineralogy concepts, descriptions, determinations, p. 431, 2nd ed. Copyright 1983 by Freeman Publishing, Inc.

Polytypism in layered silicates has been well characterized. There are as many as 19 polytypes known among micas. The repeat unit in muscovite mica, [KAl2(OH)2(Si3Al)0 o], for instance, consists of a sheet of octahedrally coordinated aluminium ions sandwiched between two identical sheets of (Si, AOO tetrahedra, the large ions being located in interlayer positions. Surface oxygens of the tetrahedra in... 

The micas have layer structures in which silicate sheets are combined with aluminate units the aluminum ions can be octahedrally as well as tetrahedrally coordinated. For example, the mica muscovite contains both octahedral and tetrahedral Al3+ ... 

Studies of hydrothermal alteration products associated with ore mineralization in acidic rocks have established the general propensity for the original minerals to be replaced by illite, sericite or hydromica in the innermost zone near the source of hydrothermal fluids and by kaolinite or expandable minerals further from the vein or center of fluid emanation. The newly-formed "mica" can be 2M, 1M, or lMd in polymorph and range compositionally from muscovite to a low potassium, silicic species which can be assimilated in the term illite (Lowell and Guilbert, 1970 Schoen and White, 1966, 1965 Kelly and Kerr, 1957 Bonorino, 1959 Tomita, e al., 1969 Yoder and Eugster, 1955 Meyer and Hemley, 1959, among many authors). 

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