Coal
noun
A stone charcoal is charcoal shaped like a little stone. Or, maybe it's often found in stone. That's coal.
せきたん
This uses the on'yomi for both kanji, so you should be able to read this on your own.
彼は、石炭ビジネスでの成功を自慢しました。
He boasted about his success in the coal business.