Serpentinization

The FIS reaction (section A3.14.3.2) has been studied in a CFUR and revealed a series of stmctiires known as serpentine patterns also, the birth, self-replication and death of spots , corresponding to regions of high concentration of particular species (see figure A3.14.17 have been observed [46]. 

Serotonin antagonist Serotomnergic agents Serotomnergic neurons Serotonin receptors Seroxat Serpak process Serpasil Serpentine... 

Sihceous matter other than clay may occur in the free state as sand, quartz fragments, and chert, and in the combined state as feldspar, mica, talc (qv), and serpentine. Metallurgical and chemical limestones should contain less than 1% alumina and 2% siUca. 

Mercury ore deposits occur in faulted and fractured rocks, such as limestone, calcareous shales, sandstones, serpentine, chert, andesite, basalt, and rhyolite. Deposits are mostiy epithermal in character, ie, minerals were deposited by rising warm solutions at comparatively shallow depths from 1—1000 m (6). 

Eig. 18. Microbolometer (a) array portion showing pixels on a 50-pm pitch. Each pixel is coimected to a readout amplifier in the supporting siUcon IC chip, (b) Detector having a 35 x 40 pm active area. The serpentine arms give excellent thermal isolation and the low mass results in a 10-ms response time, ideal... 

Forsterite. Pure forsterite is rare in nature. Most natural magnesium orthosiUcates form soHd solutions of fayaUte, Fe2Si04, and forsterite. Forsterite refractories are usually made by calcining magnesium siUcate rock such as dunite, serpentine, or oHvine with sufficient magnesia added to convert all excess siUca to forsterite and all sesquioxides to magnesia spinels. 

Talc of metasedimentary origin is formed by hydrothermal alteration of a dolomitic host rock by a silica-containing fluid. This type of deposit is typical of Montana and AustraUa. It is usually quite pure with talc content of 90 to 98% and often very white as well. Dolomite [17069-72-6], CaMg(C02)2, is the most common accessory mineral. The fourth type is of metamorphic origin, where a siUcaceous dolostone is first converted to tremolite [14567-73-8] or actinohte [13768-00-8] and then partially converted to talc. The Balmat, New York, and Death Valley, California, deposits are of this type. Tremolite, dolomite, and serpentine are common accessory minerals. This type of talc deposit has a variable talc content (30—80%), but is usually white and often commercially exploited because of the properties of its accessory minerals rather than the talc. 

Fig. 9. Methods of heating tanks (a) external heat exchanger (b) serpentine steam cods and (c) plate cods.

Chrysotile is in the serpentine mineral group aU others are amphiboles. 

The least compHcated clay minerals are the 1 1 clay minerals composed of one tetrahedral (T) layer and one octahedral (O) layer (see Fig. 1). These 1 1 clay minerals are also referred to as TO minerals. The TO package has a basal spacing (nominal thickness) of 0.7 nm (7 E) and they are commonly referred to as 7 E minerals. Kaolinite, the dioctahedral 1 1 mineral, has filling two of three octahedral sites, and serpentine [12168-92-2J, (Mg)3Si205(0H)4, the trioctahedral 1 1 mineral has filling all three octahedral sites. The kaolin minerals have limited substitution in the octahedral... 

Chrysotile (serpentine) occurs in both clino and ortho stmctures. Both one-layer ortho and clino, and six-layer ortho (as in nacrite) stmctures have been observed. Chrysotile transforms at high temperature to forsterite [15118-03-3] and siHca. Particularly fibrous varieties are called asbestos (qv). 

A number of serpentine group minerals have substitutions in both the tetrahedral and octahedral layer, but they stiU maintain electrostatic neutraUty. Amestite [12413-27-5] which approximates (Mg2Al)(SiAl)0 (0H)4 in composition, cronstedite [61104-43-3] (Fe " 2 Fe " )(SiFe " )0 (0H)4, chamosite,... 

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... 

Chlorite is another mineral that is commonly associated with mixed-layered clays. Complete soHd solutions of chlorite mixed-layer minerals have not been identified. In contrast to iUite—smectite mixed-layer minerals, chlorite mixed-layer minerals occur either as nearly equal proportions of end-member minerals (Rl) or dominated by one end member (RO) (142). Mixed-layer chlorite may consist of any of the di—tri combinations of chlorite and chlorite mixed-layering occurs with serpentine, kaolinite, talc, vermicuhte, smectite, and mica. References of specific chlorite mixed-layer minerals of varied chemical compositions are available (142,156). 

The laterites can be divided into three general classifications (/) iron nickeliferrous limonite which contains approximately 0.8—1.5 wt % nickel. The nickel to cobalt ratios for these ores are typically 10 1 (2) high siUcon serpentinous ores that contain more than 1.5 wt % nickel and (J) a transition ore between type 1 and type 2 containing about 0.7—0.2 wt % nickel and a nickel to cobalt ratio of approximately 50 1. Laterites found in the United States (8) contain 0.5—1.2 wt % nickel and the nickel occurs as the mineral goethite. Cobalt occurs in the lateritic ore with manganese oxide at an estimated wt % of 0.06 to 0.25 (9). 

A wide variety of precipitates form in cooling water systems carbonates, silicates, sulfates, and phosphates are common. Below and slightly above 212°F (100°C), calcite, aragonite, gypsum, hydroxyapatite, magnesium phosphate, anhydrite, and serpentine are commonly encountered (see Table 4.1). 

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