As archaeologists have become more interested in the relationships between settlement-subsistence systems and mobility, and more concerned with the behavioral aspects of technology, there has been an increase in studies of lithic raw materials. These studies (e.g., Gould 1979; Klippel 1971; Charlton 1978; Meyers 1970; and Novick 1978) have demonstrated that prehistoric peoples selectively utilized a wide variety of lithic materials. This variety supposedly reflects decisions on the part of prehistoric peoples to select raw materials based on physical characteristics of the rock (e.g., fracture properties, hardness, and how long the material would hold an edge), relative to the properties of the tool that was to be manufactured. However, Gould (1979) and Flannery (1976) have pointed out that not only should the physical properties of the material and tool structure be considered, but the cognitive or behavioral information that might be reflected in raw material selection also should be considered. Several ethnoarchaeologists have included this consideration in their studies of raw materials used by hunters and gatherers (Lee and DeVore 1976; Binford 1979). In his discussion of "righteous rocks" among Australian Aborigines, Gould (1979) points out that raw material variation can also carry religious and social meanings.
The region of the Piedmont where the Occaneechi and their Siouan neighbors lived is within the geological province known as the Carolina Slate Belt. In 1822, the rocks of the Carolina Slate Belt were described by Denison Olmstead as part of what he called the "Great Slate Formation" (Allen and Wilson 1968). With further geologic investigation and formation mapping, it has become clear that the Carolina Slate Belt contains both sedimentary and volcanic rocks. Although it is commonly called the Carolina Slate Belt, slate is not the major rock type in the zone, and the formation is not a single continuous belt (Butler 1963:169). The major rock units of the Carolina Slate Belt are argillite, slate, phyllite, greenstone, metamorphosed lithic-crystal tuff, devitrified glassy rocks, breccia, and volcanic conglomerate (Butler 1963:167). These rock units generally show the effects of low-grade metamorphism, and their mineral assemblages are typical of the cholorite zone of regional metamorphism (Butler 1963:169).
As detailed by Allen and Wilson (1968), the stratigraphic succession in Orange County contains four major rock units which are summarized below in ascending order.
Unit I: This unit contains predominantly amygdaloidal basalt flows intercalated with basalt porphyries and lithic and crystal tuffs.
Unit II: Andesitic to dacitic lithic and crystal tuffs characterize this unit.
Unit III: This unit is composed predominantly of felsic tuffs and lithic and crystal-lithic tuffs, with occasional flows of rhyolite and rhyolite porphyries.
Unit IV: Epiclastic argillites, laminated argillites, and graywacke predominate in this zone. Metavolcanic-metasedimentary rocks are intrusive in some areas, and rocks of Triassic age can be found in a down-faulted basin in the extreme southeastern corner of the county.
There is a wide variety of materials that could be worked into lithic tools. Rock types used by Siouans for tools include: chert (local and non-local), quartzite, vein quartz, crystal quartz, rhyolite, argillite, other metavolcanic rocks, welded tuff, vitric tuff, felsic tuff, basalt, and silicate.