Stones (usually basalt) are placed into a purpose-built Stone Heater which is filled with water. The water is typically heated to 50-53 degrees Celsius (122-127 degrees Fahrenheit).
Once the stones have heated sufficiently, some are placed onto specific points on the body (such as the back, hands, etc.) and others are held by the massage therapist and used to work the muscles.
Certain styles of stone massage also incorporate chilled stones into the routine. These stones are usually marble, and are placed into a bowl of iced water before use. A competent stone massage therapist will know when it is best to use hot stones and when it is best to use cold stones.
Also, a new type of therapeutic device called the Spa Rock, which is an electronically heated simulated hot rock, has been recently introduced.