Silicate minerals, thermal analysis

Drits V A (1975) The stmctural and crystallochemical features of layer silicates. In Ciystallochemistiy of Minerals, and Geological Problems. AG Kossovskaya (ed), Nauka, Novosibirsk, p 35-51 (in Russian) Drits VA, Besson G, Muller F (1995) An improved model for stmctural transformations of heat-treated aluminous dioctahedral 2 1 layer silicates. Clays Clay Minerals 43 718-731 Drits VA, Lindgreen H, Saly n AL (1997) Determination of the content and distribution of fixed anunonium in illite-smectite by X-ray diffraction Apphcationto North Sea ilhte-smectite. Am Mineral 82 79-87 Drits VA, Lindgreen H, Salyn AL, Ylagan R, McCarty DK (1998) Semiquantitative determination of trans-vacant and cis-vacant 2 1 layers in ilhtes and ilhte-smectites by thermal analysis and X-ray diffraction. Am Mineral 83 1188-1198... 

Although the results in Table 8 are given to the first decimal place, it is doubtful whether the method warrants such accuracy, for the errors arise, not in the calculation, but in the assumptions that are made. For example, the composition of potash mica does not always correspond exactly to the ideal formula, KAl3Si30io(OH)2, and therefore the conversion factor of Table 7 may differ slightly from the stated value. The same thing applies to other minerals. Furthermore, the clay may contain silicate minerals other than kaolinite, micas and quartz this would render the method of calculation unsound. In cases of doubt, however, the composition should be checked by thermal analysis. X-ray analysis, or both. 

DIATOMACEOUS EARTH. (Diatoma ceous silica, diatomite, Kieselguhr.) A highly siliceous mineral derived from skeletons of diatoms (microscopic organisms). Density 0.8-1.2 g/cm fusion point 1715°C. The material s closed cells and high porosity provide a low density and low thermal conductivity. Diatomaceous earth is mined in California, Nevada and Arizona. A typical analysis 85.3% silica, 5.4% alumina, 1.1% FejOj, 1.1% calcium carbonate, 5.6% moisture. 

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