flint
/flɪnt/noun
mass noun
1- a hard grey rock consisting of nearly pure silica (chert), occurring chiefly as nodules in chalk黑燧石, 燧石, 火石。
1.1
- count noun a piece of this stone, especially as flaked or ground in ancient times to form a tool or weapon（尤指远古工具或武器）燧石石器。
1.2
- 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（明火枪用的）打火石, （打火机用的）电石。
1.3
- used in expressing how hard and unyielding something or someone is（人）铁石心肠, （物）坚如燧石：
mean faces with eyes like flints.
一张张充满恶意的面孔, 目光尖利无情。
词源
Old English; related to Middle Dutch vlint and Old High German flins.