Feldspars mixing properties

Carpenter M. A. and Ferry I M. (1984). Constraints on the thermodynamic mixing properties of plagioclase feldspars. Contrib. Mineral Petrol, 87 138-148. 

Waldbaum and Thompson (1969). The mixing properties for sanidine -high albite solutions derived by Thompson and Waldbaum (1969a) are used to construct feldspar phase diagrams. The equations of state for alkali feldspar are used to predict equilibria involving reactions among feldspar and other phases (including feldspar liquids) at various temperatures and pressures. 

The presence of impurities in raw materials reduces to some extent the temperature of formation of eutectic melts, simultaneously broadening the sintering interval. Addition of feldspar is very effective in this direction. Feldspar is used in raw material mixes for those steatite products which do not have to meet particularly stringent requirements for electrical properties. 

A phase is a restricted part of a system with distinct physical and chemical properties (Wood and Fraser 1976). A phase can also be defined as a physically and chemically homogeneous portion of a system with definite boundaries (Brownlow 1979). These attributes mean that a phase should be mechanically separable from a system. Example phases are minerals and well-mixed gases and liquids. Not true phases, because they are comprised of more than one mineral, are rocks such as granite or minerals such as the feldspars when they are chemically zoned and have spatially variable compositions. 

In a survey of U.S. stream sediments, Kennedy (1965) concluded that the makeup and properties of the stream sediments essentially equaled that of local soils. In the eastern states (50 to 150 cm precipitation), dominant clays in the <4 jum (0.004 mm) fraction were illite, kaolinite, ver-miculite, and interlayered clays, with a CEC of 14 to 28 meq/lOOg. In central and west-central states (25 to 100 cm precipitation) Kennedy found dominant smectite, vermiculite, mixed-layer illite, kaolinite, quartz, and feldspar in the <4 /zm fraction, with a CEC range of 25 to 65 meq/100 g. In California and Oregon, because of the wide range of wet and dry conditions (<25 to >200 cm precipitation), clays were highly variable, and had a range of CEC s from 18 to 65 meq/l(X) g for the <4 /um fraction. 

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