Pyroxene Crystalline Solution

Abstract

Orthopyroxene is one of the few important rock-forming minerals that can be considered as quasi-binary without significant loss of accuracy. Usually more than 95% of the mineral is a crystalline solution of the end members enstatite (MgSiO₃) and ferrosilite (FeSiO₃). Fe²⁺ and Mg²⁺ are distributed between two nonequivalent sites M 1 and M 2. With the use of X-ray or Mössbauer spectroscopic technique, it is possible to determine the proportion of Fe²⁺ in the two nonequivalent sites (Evans, Ghose and Hafner, 1967). These data can be used with the help of suitable solution models to determine the thermodynamic properties of the solution (Virgo and Hafner, 1969; Saxena and Ghose, 1971).