Synthesis of a non-stoichiometric pyroxene under ambient pressure

Abstract

Crystallization experiments were carried out on powdered glasses having the composition Di₂₃Es₅₃An₂₄ at temperatures of 1250, 1275, 1300, 1325 and 1350°C. The resulting crystalline phases are clinopyroxenes and a trace of unknown oxide crystals. The pyroxenes grown at 1325 and 1350°C are stoichiometric clinopyroxenes rich in Al and Fe. Those grown at the lower three temperatures are non-stoichiometric clinopyroxenes which are extremely rich in Al and contain only negligibly small amounts of Mg. Non-stoichiometric clinopyroxenes are shown not to be characteristic products of high pressure conditions.