Prismatic blade
This dark grey rectangular obsidian flake was used in the Fayyum region of Egypt during the Predynastic Period. Obsidian can be knapped to a very thin and very sharp edge, suitable for cutting hides and meat, and probably many other uses.
Obsidian was such a valuable and useful substance that it was traded over long distances, coming to Egypt from East Africa, and possibly from the Aegean and West Asian.