Nearly 20,000 pieces of lithic were recovered from Project SIN. Of these the great majority (97%) were of a white chert, although it was sometimes identified as chalcedony because some examples had a more translucent surface. The next most abundant lithic material was a reddish chert with whitish inclusions (2%). 61 pieces of obsidian were recovered, about 0.3% of the total assemblage.
White chert awl Red chert projectile point
Unutilized flakes were by far the most abundant material (80% of total), suggesting that lithic production was practiced on site. The next most numerous type were microlith scrapers, dubbed 'raspaditas,' which accounted for about 12% of the total lithic assemblage. These were made exclusively of the white chert, and as discussed in the section on Food Preparation were likely used to process root crops such as manioc. Seventy-six projectile point fragments were found, and interestingly about 1/3 of these were of the red chert, suggesting a strong preference for that material for the larger and more complex lithic tools.