These mugs are made from a unique craftwork process. The dry serpentinite is hammered into powder and mixed together with clay in a ratio of 70% serpentinite to 30% clay, which allows for sturdy yet statuesque shaping. After being fired in a kiln, each piece is covered with leaves. The smoke from the leaves against the hot serpentinite creates the dark, radiant finish. All pieces are microwave and dishwasher safe.