Abstract
Experimental evidence is presented for a process of mineral alteration at elevated temperatures in which the change in moment due to alteration is a constant fraction of the moment induced by a laboratory field. Alteration of this nature will result in a linear Arai plot, and has probably escaped detection in the past. A method for estimating its magnitude is outlined, and applied to results obtained using well-dated sherds from Tel-el-Amarna. Removal of the effect of alteration reduces the scatter in the data from 29% to 6%.
