Point Defects in Minerals

Abstract

All crystals have point defects that are formed as the consequence of both thermal activation and aliovalent impurities. Properties such as diffusion, creep, and electrical conductivity have been shown to depend on point defects in all types of crystals. This has been demonstrated well for olivine, for example [Jaoul et al. 1980; Ryerson et al. 1987; Kohlstedt and Hornack 1981; Hermeling and Schmalzried 1984; Schock et al. 1989; Bai et al. 1991]. The minerals pyroxene [Duba et al. 1973; Huebner et al. 1979] and spinel, as well as polymorphs of these minerals and olivine [Hirsch & Shankland 1991], which are stable at higher temperatures and pressures, are also likely to have their physical properties determined by point defects [Paterson and Kekulawala 1979; Linker et al. 1984]. The mechanical properties of quartz, the dominant constituent of the crust, are also related to point defect concentrations.