A stone massage is a massage that uses smooth, flat, and heated rocks placed at key points on the body. Stones (usually basalt) are placed into an electric slow-cooker or a purpose-built device which is filled with water. The water is typically heated to 52-54 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.