A heatstone is a round or oval piece of volcanic glass that weigh anywhere from 2 to 4 pounds each. Depending on the outside temperature, a heatstone can heat anywhere from a twenty to forty foot square area. These stones last three years before they lose their warmth, and must be replaced. This fact keeps their value up in the colder regions of the world. These magical stones are formed naturally in Qadira, where these who wander the desert collect them to sell in Katheer.