- Hard quartz - Hard stone - Stone age axe material - A massive, somewhat impure variety of quartz, in color
usually of a gray to brown or nearly black, breaking with a conchoidal
fracture and sharp edge. It is very hard, and strikes fire with steel. - A piece of flint for striking fire; -- formerly much used,
esp. in the hammers of gun locks. - Anything extremely hard, unimpressible, and unyielding, like
flint.