Biotites

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 ... 

Property Muscovite Phlogopite Biotite Synthetic fluorophlogopite... 

In all cases, water and carbonic acid, the latter of which is the source of protons, are the main reactants. The net result of the reaction is the release of cations (Ca " ), Mg ", K", Na" ) and the production of alkalinity via HCO. When ferrous iron is present in the lattice, as in biotite, oxygen consumption may become an important factor affecting the weathering mechanism and the rate of dissolution. 

Regularly interstratified (1 1) chlorite and vermiculite has been attributed to the mineral corrensite [12173-14-7] (141). Chlorite mixed layers have been documented with talc, vermicuhte, smectite, iUite, biotite, kaolinite, serpentine, and muscovite. The mixed-layer mineral is named after the components, eg, talc—chlorite. The eadier Hterature, however, has reference to specific minerals such as kulkeite [77113-95-2] (talc—chlorite and tosudite... 

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). 

The OH can be partly replaced by F and, in phiogopite, partial replacement of Mg by Fc gives biotite (black mica) [K(Mg,Fe )3-(OH.F)2(Si3AlOio)l. The presence of K between the layers makes the micas appreciably harder than pyrophyliite and talc but the layers are Mill a source of weakness and micas show perfect cleavage parallel to the layers. With further... 

Magnesia-beize,/. Dyeing) magnesia mordant, -gehalt, m. magnesia content, -glimmer, m. magnesium mica (biotite). 

Sorption of plutonium (l.fixlO-11 M) and americium (2xl0-9 M) in artificial groundwater (salt concentration 300 mg/liter total carbonate 120 mg/liter Ref. 59) on some geologic minerals, quartz, biotite, o apatite, o attapulgite, montmorillonite. Dashed lines indicate the range for major minerals in igneous rocks. Experimental conditions room temperature, particle size 0.04-0.06 mm, solid/liquid ratio 6-10 g/1, aerated system, contact time 6 days. 

Pyrophillite, talc, muscovite, and biotite have the following sequence of atom-planes along the pseudo-hexagonal axes ... 

Associated minerals include other clays, garnets, biotite and quartz. 

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). 

Quartz, biotite, muscovite, and hornblende are common and barite and cordielite are also found in some ores (Kanehira and Tatsumi, 1970). 

Hydrothermal alteration minerals from midoceanic basalt are analcite, stilbite, heulandite, natrolite-mesolite-scolecite series, chlorite and smectite for zeolite facies, prehnite, chlorite, calcite and epidote for prehnite-pumpellyite facies, albite, actinolite, chlorite, epidote, quartz, sphene, hornblende, tremolite, talc, magnetite, and nontronite for green schist facies, hornblende, plagioclase, actinolite, leucoxene, quartz, chlorite, apatite, biotite, epidote, magnetite and sphene for amphibolite facies (Humphris and Thompson, 1978). 

Figure 12 continued, (d)-(g) Mineral isochrons for rhyolites from the Olkaria volcanic center (Kenya), (d) and (f) alpha spectrometry resnlts from Black et al. (1997). (e) and (g) TIMS resnlts from Henmaim and Davies (2002). All the rhyolites have eraption ages between 3.3 and 9.2 ka. Note that the same sample (570) analyzed in both stndies gives rather different ages (f and g). Same abbreviations of mineral names as in Fignre 10 + Qz qnartz KF alkali feldspar Amph amphibole Bt biotite. 

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