Good Riddles

Question: 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?

Question: He has married many women, but has never been married. Who is he?

Question: Can a man legally marry his widow's sister in the state of California?

Question: A cowboy rode to an inn on Friday. He stayed two nights and left on Friday. How could that be?

Question: I am greater than God, more evil than the devil, the poor have me, the rich don't, and if you eat me, you'll die.What am I?