THE USE OF MINERALOGY TO IDENTIFY SOURCES OF SOAPSTONE ARTEFACTS: AN EXAMPLE FROM SOAPSTONE RIDGE, GEORGIA (USA)

摘要

The late Archaic Soapstone Ridge quarries, near Atlanta, Georgia, are the largest sources of archaeological soapstone in the south-eastern USA. Ten soapstone artefacts from the coastal plain, over 200 km south of Soapstone Ridge (SSR), were used in an attempt to relate their mineralogy to that of the Soapstone Ridge quarries and to investigate the utility of mineralogy in the sourcing of soapstone. There is an overall similarity in the abundance of the major soapstone minerals, talc, chlorite and amphiboles in the artefacts and the SSR soapstone. Differences in the variety of amphibole (tremolite/actinolite, magnesiohornblende and magnesiocumingtonite/anthophyllite) and FeTi oxides (magnetite and ilmenite) eliminate SSR as a source for some of the artefacts. The compositions of chlorite (Cr), magnesiohornblende (Si, Al) and Fe oxides (Cr, Mn) in other artefacts are not consistent with a Soapstone Ridge source. The talc compositions are identical in the artefacts and the SSR soapstone. The mineral assemblage and compositions of two artefacts are consistent with a Soapstone Ridge source. Despite an overall similarity in the modal mineralogy of the artefacts and Soapstone Ridge quarries, there is enough diversity to distinguish between artefacts from Soapstone Ridge or some other source. Mineralogy is a useful tool for the evaluation of soapstone sources.