Microdrill

A microdrill is a very small chipped-stone drill made on a microblade, a narrow, parallel-sided flake struck from a small prepared core. One end is shaped into a slender, needle-like bit; the rest of the blade is barely altered. At Cahokia, microdrills occur together with the microcores and unmodified microblades from which they were made (Yerkes 1983), part of a microblade industry first reported there by Mason and Perino (1961).

Workers struck microblades from small chert cores and turned them into drills by narrowing one end to a point (Arnold 2012). The finished drill was set in a handle: Island Chumash bead makers in California hafted chert microdrills on wooden dowels and drilled shell blanks resting on a sandstone slab or wooden tablet (Arnold 2012).

Microwear study of microdrills from Powell Mound and the Dunham tract at Cahokia showed polish and damage from drilling shell almost exclusively, whereas Jaketown perforators from Poverty Point had worked a range of materials (Yerkes 1983). The Illinois State Museum links microdrills to the making of freshwater and marine shell beads and ornaments and notes that they are uncommon on Woodland sites. On the Channel Islands they perforated Olivella shell disk blanks 4–12 mm across (Arnold 2012). The key trait is a needle-thin drill bit shaped on the end of a microblade.

Best documented in the American Bottom of Illinois at Cahokia (Powell Mound, Dunham tract, Kunnemann Mound) and the Lohmann site (Yerkes 1983; Illinois State Museum). A separate microdrill industry served shell-bead making on the northern Channel Islands of southern California (Arnold 2012).

Identification tips: Look for a blade blank, with parallel edges and one or two ridges running down one face, and with only the tip reshaped. Microdrills turn up with microcores, unworked microblades and shell artifacts (Yerkes 1983).

Similar types: Drill / Perforator is usually chipped on both faces, often from a reworked point with a shaped base, and most are 40–80 mm long (Bell 1980). Jaketown perforators of the Late Archaic Poverty Point culture are also tiny tools on blades and flakes, but they have one bulbous end and a short point (Gibson 1983).

Naming: "Microdrill" is the standard term in the Cahokia literature (Yerkes 1983); the tools belong to the wider class archaeologists call microliths.

Dating evidence: Microdrills are reported from the Early Mississippian Lohmann site (Esarey and Pauketat 1992) and from Kunnemann Mound at Cahokia (Pauketat 1993), as summarised by the Illinois State Museum.