Hydrated Sulfates in the Sydney Coalfield, Cape Breton, Nova Scotia

Abstract

Hydrated sulfates associated with decomposition of pyrite and copper-iron sulfides occur in coal in contact with the atmosphere. Melanterite, rozenite, epsomite, pickeringite, halotrichite, aluminocopiapite and sideronatrite were identified from coal seams and mines in the Sydney coalfield. This is apparently the first reported occurrence of sideronatrite and alumino-copiapite in North America, and for the remaining minerals with the possible exception of melanterite, first occurrences from Cape Breton. Crystallization of melanterite, and possibly of other hydrated sulfates, contributed substantially to the mechanical instability of coal faces in old underground workings by erosion of supporting pillars. In addition, alunite, jarosite, natrojarosite and barite (?) were tentatively identified from the Evans coal mine situated in a Carboniferous basin somewhat older than the Sydney basin. These sulfates are associated with the decomposition of copper-iron sulfides and possibly pyrite. All minerals were identified by X-ray powder diffraction.