Unusual weathering products of oldhamite parentage in the Norton County enstatite achondrite

Oldhamite, CaS, is found only in enstatite chondrites and enstatite achondrites. During the course of a comprehensive study of Norton County, oldhamite was found in several polished thin sections of enstatite achondrite. Inspection of thousands of specimens of Norton County showed that occasionally white, pale-yellow and brown specks, generally a few millimeters in size, occur on their surfaces. X-ray powder analysis of these materials shows that they contain portlandite, Ca(OH)2, vaterite (CaCO3, hexagonal), calcite (CaCO3, trigonal), bassanite (CaSO4 1/2 H2O) and one unknown species. It is suggested that these minerals were produced by terrestrial weathering of oldhamite.