Exploratory Studies into Possible Uses of Calcareous Dolostone

Abstract

Excavations at habitation sites on the Shivwits Plateau, northwestern Arizona suggest that calcareous dolostone was regularly procured and used by the prehistoric inhabitants of that region. Calcareous dolostone, a soft, powdery carbonate rock composed of the minerals dolomite and calcite, is not local to these sites but crops out some four to six kilometers from the site. Its presence at the sites, therefore, indicates its intentional procurement for some as-yet undetermined purpose. To investigate how the material might have been used, a series of archaeological experiments were conducted to evaluate possible functions suggested by ethnographic analogy. Specifically, we evaluated the performance characteristics of powdered dolostone with reference to three activities: clay processing, pigment production, and the production of architectural plaster. Our results suggest that, as a clay additive, dolostone improves the texture of the sticky Shivwits Plateau clays; and that, when mixed with appropriate binders, it produces a durable pigment that could have been used as a paint. Our attempts to produce a waterproof and weather resistant plaster, in contrast, failed, although our results suggest that the dolostone could produce a thick whitewash appropriate for painting room interiors.