Macroscopic and petrographic identification of the rock types used for stone tools in central Connecticut

Date of Completion

January 1991


Anthropology, Archaeology|Anthropology, Cultural|Geology




Macroscopic examination of 24 lithic assemblages and microscopic analysis of assemblage waste flakes prepared in thin section have provided new information about the materials quarrier-knappers used in central Connecticut. Throughout prehistory they relied primarily upon locally available quartz, quartzite, basalt and hornfels from rock exposures and glacial drift.^ The major sources of basalt and hornfels in the state are the large basalt exposures and the metamorphosed contact margins underlying the second and third lava flows of a ridge that bisects the state, north to south. This centralized source of two different rock types provided the opportunity to trace the distribution of a local tool materials across the region east and west of the ridge. As expected, the data show concentrated use at sites nearest the ridge with an attenuation in the frequency of occurrence with distance from the ridge.^ Identifying all the assemblage rock types macroscopically or with the aid of low power (10X) magnification proved to be problematic especially for artifact rocks with weathered rinds. Weathering also interfered with analysis by X-ray fluorescence because the exterior rind was chemically different from the interior fresh rock of specimens tested. Only in thin section could these materials be identified and sourced accurately.^ The waste flakes sacrificed for petrographic analysis proved to be such a rich storehouse of information that the research potential of waste flake analysis is especially promising. Suites of waste flakes sampled from each assemblage analyzed petrographically revealed not only the diversity in the local and non-local material selections but also provided supporting evidence of more than one rock type imported to a site from the same region.^ Macroscopic analysis provided suitable data for comparing materials used through time and with distance from the lithic sources. However, only through microscopic analysis of flake thin sections could the diversity and fine-grained quality of quarrier-knappers' selections be appreciated. ^