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 very hard, fine-grained quartz that sparks when struck with steel.
- A piece of flint used to produce a spark.
- A small solid cylinder of a spark-producing alloy, used in lighters to ignite the fuel.
- A piece of flint used as a tool by prehistoric humans.
- Something resembling flint in hardness: a jaw of flint.