Publication Date:
2007-12-21
Description:
A large number of polished stone implements from Palaeolithic to Bronze Age sites of Northern Italy and Southern France are made of high-pressure (HP) metamorphic rocks (eclogite and related rocks), mainly consisting of Na-pyroxene (jadeite to omphacite) from the metamorphic belt of the Western Alps. The standard archaeometric study of prehistoric stone implements follows a procedure that is invasive, expensive and time-consuming. Since Na-pyroxenes may show a large compositional range, a thorough study of the variations affecting thedhklvalues, obtained by X-ray diffraction, of three selected reflections as a function of different chemical composition was carried out, in order to determine the chemistry of Na-pyroxene isomorphic mixtures and roughly evaluate their relative amounts. These reflections ( ar221, 310, 002) are sharp, intense and sensitive to the variation of pyroxene chemical composition. Using suchdhklvalues measured on pyroxenes of known chemistry, a Ca-pyroxene(Di)–jadeite(Jd)–aegirine(Ae) compositional diagram was constructed, from which the composition of an unknown pyroxene can be estimated within an error of about 5%. When the size of the object is relatively small and a flat polished surface is present, the proposed analytical procedure becomes totally non-invasive. The data obtained shed light on the provenance sources of such implements and the prehistoric trade routes.
Print ISSN:
0108-7673
Electronic ISSN:
2053-2733
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
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