Mine To Wooden Case

Riddle: I am taken from a mine and shut up in a wooden case from which I am never released, and yet I am used by almost everybody. What am I?

Answer: Pencil Lead.

Source: https://www.riddles.com/7806

I am taken from a mine and shut up in a wooden case from which I am never released, and yet I am used by almost everybody. What am I? — Mine to Wooden Case by Chris Oliver v1.

Riddle: I am taken from a mine and shut up in a wooden case from which I am never released, and yet I am used by almost everybody. What am I? Answer: Pencil Lead. — by Chris Oliver v2.