Blue Vivianite in Prehistoric Clay

Abstract

Experiments have demonstrated that vivianite, when processed using heat, produces a vivid blue pigment that could have been used as body paint, yet this vivid blue pigment could have been utilized in other ways as well. Archaeologically, vivianite has been documented as a component of clay pottery, but this vivianite was part of the clay matrix, not applied to the surface of the vessel. Experiments designed to assess the utility of vivianite as a blue colorant to a prehistoric ceramic matrix are outlined here. Clay pellets were painted with a vivianite slip and alternately had vivianite added to the clay prior to drying. Contrary to expected results, this vivianite, when mixed with clay or applied to the surface, does not yield a vivid blue color with heating. As a result, we must assume that vivianite may have merely been an accidental inclusion in the clay matrix as documented archaeologically, perhaps as a naturally occurring component of the original clay source or tempering material.