Hot stone massage is a natural therapy in which warmed stones are positioned on parts of the client's body of to maximize the therapeutic benefit. The stones used are typically river rocks or other very smooth-surfaced stones made of basalt. These stones are heated in sanitizing water before use. The high iron content in basalt helps the stones retain heat during the massage. Hot stone massages are beneficial on both physical and psychological levels. Always check with your doctor before getting a hot stone massage; individuals with certain conditions--including pregnant women and people with high blood pressure--are advised to avoid this type of therapy.