flint

noun

• a hard grey rock consisting of nearly pure silica (chert), occurring chiefly as nodules in chalk: houses built of brick and flint [as modifier]:flint implements
• [count noun] a piece of flint, especially as flaked or ground in ancient times to form a tool or weapon: the early settlers also found a ready supply of flints in the chalk cliffs
• [count noun] a piece of flint used with steel to produce an igniting spark, e.g. in a flintlock gun, or (in modern use) a piece of an alloy used similarly, especially in a cigarette lighter: he struck a light with his flint