Melting Stones — Tamora Pierce

An apprentice mage. A dying land. An impending disaster.

Four years have passed since Evvy left the streets of Chammur to begin her training as a stone mage. At fourteen, she's unhappy to be on a new journey with her mentor, prickly green mage Rosethorn, who has been called to the Battle Islands to determine why the plants and animals there are dying. Evvy's job is to listen and learn. but she can't just keep quiet and do nothing. With the help of Luvo, the living stone heart of a mountain, Evvy uncovers an important clue. Now, with the island on the brink of disaster, it's up to Evvy to halt sheer destruction.