Why does flint spark?

Answer 1

When you rub steel against a very hard, sharp rock such as flint, it cuts very tiny flakes of the steel off and a high amount of heat is created by the great friction. When the tiny flakes of steel are heated, they combust thus showing the spark.

Answer 2

Flint sparks when the steel rubs up against it and cuts tiny pieces of flint and the friction heats the tiny pieces of flint and they combust (explode) thus, showing the spark