PHYSICAL PROPERTIES OF SYNTHETIC AND NATURAL PYROXENES IN SYSTEM DIOPSIDE-HEDENBERGITE-ACMITE

Unit cell dimensions and refractive indices have been determined for synthetic pyroxenes in the system CaMg Si//2O//6-CaFeSi//2O//6- NaFeSi//2O//6, which have been crystallized and annealed on the nickel-bunsenite (Ni- NiO) oxygen buffer curve at 700 C and a total pressure of 2 kbar. The data presented confirm the many postulates that a complete solid solution series does exist in the subsolidus region of the 'ternary' system. The unit cell dimensions show an almost linear change with composition between the end members. The determined cell parameters for a series of analyzed natural alkali pyroxenes have been compared with the data for the synthetic pyroxenes.