The NSS Bulletin - ISSN 1090-6924
Volume 41 Number 4: 126-127 - July 1979
A publication of the National Speleological Society

Recent Anhydrite and Bassanite from Caves in Big Bend National Park, Texas
Carol A. Hill

Abstract

Recent anhydrite (CaSO4) amd bassanite (CaSO4•H20) occur as white crust on the walls and ceilings of three small caves in Big Bend National Park, Texas. Originally precipitated from groundwater as gypsum (CaSO4•2H2O), these crusts subsequenclty changed to bassanite and then to anhydrite in the absence of a liquid phase. High cave temperatures (up to 35°C) and low relative humidities (10 to 60%) caused dehydration of the gypsum. This is the first reported occurrence of bassanite and anhydrite as cave minerals.

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