I come from a mine and get surrounded by wood always. Everyone uses me. What am I? (9/31)

This should be a simple riddle for many of you, as this riddle is popular among kids. The definition of a mine could lead you to coal or diamonds. Your best clue is the wood detail. If you have not heard this in your childhood, this riddle could be tricky. But the wood detail will guide you. The answer is the ‘pencil lead.’