gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1947.028.198.06 The Relationship of Orthopyroxene to Pigeonite Poldervaart Arie M.Sc., Ph.D. Geology Department, University of Cape Town

Communicated by Prof. F. Walker

 9 1947 28 198 164 172 Copyright © 1947, The Mineralogical Society 1947 Abstract

A new classification of the orthopyroxene series is suggested. Two analyses of magnesian orthopyroxenes are given, and curves are drawn to correlate the chemical composition with the optical properties. The stability fields of orthopyroxenes and pigeonites are discussed in detail.