Abstract

Mafic pegmatites cut serpentinite in Precambrian gneisses. Three varieties contain (a) vermiculite only; (b) vermiculite and corundum; or (c) calcic plagioclase, vermiculite, and corundum (plumasitic type). Chemical compositions suggest a trend from anorthosite through plumasite to vermiculite-corundum pegmatite. The absence of primary olivine suggests emplacement temperatures below 500 degrees C. Gems are rubies and sapphires.

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