ANALCIME CRYSTALLIZATION AND COMPOSITIONAL PROFILES—COMPARING APPROACHES TO DETECT POST‐DEPOSITIONAL ALTERATIONS IN ARCHAEOLOGICAL POTTERY*

TLDR

Comparative studies and profile measurements are routinely used to detect post‑depositional alterations in ceramics, and both were applied to two sets of Roman pottery containing altered pieces. The study employed neutron activation analysis and X‑ray diffraction to analyze the pottery. The two methods produced markedly different results, indicating that they detect distinct alteration levels and should be used together; in particular, glassy phase decomposition followed by Na‑zeolite analcime crystallization rapidly alters high‑fired calcareous pottery, potentially compromising archaeometric analyses.

Abstract

The approaches of comparative studies and profile measurements, often used in order to detect post‐depositional alterations of ceramics, have been applied simultaneously to two sets of Roman pottery, both of which include altered individuals. As analytical techniques, Neutron Activation Analysis and X‐Ray Diffraction have been used. Both approaches lead to substantially different results. This shows that they detect different levels of alteration and should complement each other rather than being used exclusively. For the special process of a glassy phase decomposition followed by a crystallization of the Na‐zeolite analcime, the results suggest that it changes high‐fired calcareous pottery rapidly, and so fundamentally that the results of various archaeometric techniques can be severely disturbed.