BH d 
tee ARCHEOLOGY IN BRITISH GUIANA 129 
Ovacid 2 CM 
Ficure 51.—Koriabo Phase stone tools. a, Adz. , Chisel. c, Flake blade. 
Chisel (fig. 51, 6).—A well polished chisel of gray-green quartzite 
measures 5.8 cm. long, 1.7 cm. wide at the center, tapering to bit an 
butt ends only 0.9 cm. wide. 
Choppers.—Crudely shaped choppers made by percussion blows on 
a quartzite cobble are represented by fragments too small for recon- 
struction of original dimensions. 
Flake blades and knives (fig. 51, c) —Percussion flakes struck from 
quartzite and quartz have one side abraded to form a cutting edge. 
The flakes are small and irregular in form, measuring 3.8 cm. in di- 
ameter and 4 by 8 cm. 
Mano.—A fragment of extremely fine-grained micaceous schist was 
used for grinding. It shows no intentional shaping, but the edges are 
