Some orthopyroxenes from Scottish metamorphic rocks

Abstract

SummaryChemical analyses, cell parameters, and optical properties are presented for seven Scottish orthopyroxenes: four from Harris, two from Scourie, and one from Belhelvie, Aberdeenshire. The compositions range from En83·6 to En55·5. Six of the orthopyroxenes are from pyroxene granulites or related rocks and the other is from a plagioclase-hypersthene hornfels: the latter mineral is notable in having 7·21% Al2O3, causing a considerable contraction in the a and b cell parameters. The alumina content of orthopyroxenes is briefly discussed. Analyses are also given for olivine and diopsidic augite from a South Harris ultrabasic gneiss and for two enderbitic pyroxene gneisses from Scourie.