Flint is an item from vanilla minecraft used in many crafting recipes. It can be created by mining Gravel.
It is also available by transmuting 4 cobblestone together with a Minium Stone.
This is a shapeless recipe. I'm not sure of the number produced.
IndustrialCraft2 macerator Recipe
It is a useful source of "Instrumentum" for use with the Thaumcraft 3 mod.