Hard Riddles with Answers for Serious Thinkers

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 every person. What am I?

I go in dry and come out wet, the longer I am in, the stronger I get. What am I?

What flies without wings, and cries without eyes?

I have cities but no people, forests but no trees, and rivers but no water. What am I?

The person who makes it has no need of it. The person who buys it has no use for it. The person who uses it cannot see it. What is it?

You measure my life in hours and I serve you by expiring. I am quick when I am thin and slow when I am fat. What am I?

I have keys but open no locks, I have space but no room, you can enter but you cannot go inside. What am I?

I am not alive, but I grow; I do not have lungs, but I need air; I do not have a mouth, but water kills me. What am I?

What five-letter word becomes shorter when you add two letters to it?

I am seen in the water, but never get wet. What am I?

What has a heart that does not beat?

I can be cracked, made, told, and played. What am I?

Two girls were born to the same mother on the same day at the same time, in the same month and year, yet they are not twins. How?

What English word has three consecutive double letters?

I am always hungry and will die if not fed, but whatever I touch will soon turn red. What am I?