TALC-SCHISTS AND ALTERED IGNEOUS AND METAMORPHIC ROCKS: PREHISTORIC QUARRYING AND UTILIZATION IN NEW ENGLAND
The convention among archaeologists is to assign the lithologies used in the production of stone bowls as steatite. The use of the term is not aligned with geologic usage. The geologic classification of many of these lithic objects falls broadly in the categories of altered igneous and metamorphic rocks. Petrologic studies indicate stone utilized for bowl production during the archaic period (3-5kya) are altered by metasomatic processes and had meta-sedimentary and/or meta-volcanic protoliths. These include among others, amphibolites, calc-silicates, and schists. Highly altered granitoid, dioritic, and gabbroic rocks were also used. The principal focus of Prehistoric bowl production was malleability, and thermal resilience.
Prehistoric quarries frequently used the same talc-schists that were exploited in Historic soapstone production. These Prehistoric quarries, worked stones, and ledges generally cover many acres. The associated suite of tool marks include: pecked grooves along cracks and foliations; deeply pecked notches; and pecked xenoliths and vugs. The in-situ talc-schist bowl preform found in Hillsborough Co., NH in October 2004 associates the grove and notch techniques used in quarrying ledge and boulders with prehistoric bowl production. This same suite of tool marks has recently been found in association with leucocratic altered igneous rocks. These new sites have dozens of pecked circles. These discoveries indicate that the variety of materials and the geographic extent of Native American utilization of lithic resources are greater than previously assumed.