After seeing all the threads people made because they forgot a book I feel a little disheartened...but who knows! Here goes. Fantasy of a world of people who exploit this fire stone, so the sky turns to ash. These people have never seen the sky. Some people are forced to mine, who I think don't have magic to tap into this fire stone, while others, who I think can tap into the magic of the fire stone, live in luxury. Main character is a woman, I think, who was a miner but was found to have the magic. She was taken and I don't remember the rest. What I do remember is the magic rocks of fire, and a really cool little italicized description of what happened to the world because the stone was exploited so much. I'm done searching, I leave it to you. Reminds me of The Last Book in the Universe, which is a great book btw.