flint
noun /flɪnt/
  /flɪnt/
- [uncountable, countable] a type of very hard grey stone that can produce a spark when it is hit against steel; a piece of this stone
- prehistoric flint implements
 - His eyes were as hard as flint.
 
 - [countable] a piece of flint or hard metal that is used to produce a spark
 
Word OriginOld English; related to Middle Dutch vlint and Old High German flins.