Oldowan stone tool. Prehistoric stone tool being held in a hand. This stone tool is from the Oldowan stone tool industry, or Mode I, an early and primitive form of stone tool. The name comes from Olduvai Gorge, Tanzania, where the first such tools were discovered. The peak usage dates to between 2.4 and 1.7 million years ago, mostly in Africa but also spreading to Asia and Europe. Rocks such as basalt and flint were used to make these tools, with roughly formed edges and surfaces used for scraping, chopping, boring, and hammering. Photographed in Olduvai Gorge, Tanzania.