- The conchoidal fracture of chert is the basis of the stone edge.Photo (c) Andrew Alden, licensed to About.com (fair use policy)
- Obsidian is the ultimate material for stone tools.Photo (c) Andrew Alden, licensed to About.com (fair use policy)
- René Castanet knaps flint at his museum in Sergeac, in the Dordogne where prehistoric sites abound.Photo courtesy Paul Lahaie, all rights reserved