flint

An impure quartz rock, usually gray, brown, or black, abundant in Palestine. It fractures on conchoidal lines and holds an extremely sharp edge, either smooth or serrated. It was used for a variety of tools, such as awls, axes, knives, picks, scrapers, sickles, and weapons (arrowheads and spear points). Knives used for circumcision were made of flint (Exod 4:25; Josh 5:2; Josh 5:3). Flint serves as a metaphor for sharp-cutting destructive power (Isa 5:28) and stubborn faithfulness (Isa 50:7) and is a dubious source of water (Ps 114:8; Deut 8:15). It can be manipulated by humans (Job 28:9), but is a most unlikely source of any nourishment (Deut 32:13).