flint

Old English flint comes from Proto-Germanic flintaz, and its deeper roots are uncertain—possibly connected to a root meaning to split or to strike. The word names a cryptocrystalline form of quartz that fractures with sharp, conchoidal edges when struck. This property made flint the defining material of human prehistory. Homo habilis was knapping flint tools in East Africa two million years ago.

Flint's importance to human civilization is difficult to overstate. Stone Age cultures from every inhabited continent used flint for blades, scrapers, arrowheads, and axes. The quality of local flint determined the prosperity of settlements. Grimes Graves in Norfolk, mined from roughly 3000 to 1900 BCE, is one of the earliest known flint mines—a Neolithic industrial site where thousands of shafts were sunk to reach the best seams.

When iron replaced flint for tools, flint found a second career: fire-starting. Striking flint against iron pyrite or steel produces sparks hot enough to ignite tinder. The flintlock musket, developed in the early 1600s, used a piece of flint to strike a steel frizzen and ignite gunpowder. For two centuries, armies fought with flintlock weapons. The stone that made the first knives also fired the first rifles.

The word flinty entered English as an adjective meaning hard, unyielding, pitiless. A flinty stare, a flinty determination. The metaphor works because everyone who has ever handled flint knows it: cold, hard, sharp, unyielding. It cuts you if you are careless. It does not care.