Gemstones originate from hot magma inside the earth and are formed from dust, sand, chemical substances and acids that have dissolved in water. Historically, gemstones were believed to have protective and talismanic properties and to keep evil spirits away as well as effectiveness in certain types of healing.
Gemstones are divided into three basic categories: rough stones taken from the original rock and allowed to remain in their natural condition. Being free from the imprint of human workmanship, unbridled energy is believed to flow through them and they possess the greatest healing power. It is recommended that rough stones be placed directly upon the body.
The second category is tumbled stones. For this type of gemstone, rough stones are put with water and sand in a drum that is then turned. Tumbled stones are rounded with smooth surfaces and are often used as touchstones. They are best suited to be laid or pressed onto the body. It is believed that by holding and rubbing these stones, their energy passes through the hand and the body becomes infused with their power.
The third major category is gemstones made into jewelry. The precious metals in which they are set are believed to increase the energy level of the stone. Gold settings will enhance the power of every stone. Silver strengthens the vibratory intensity of coral and turquoise. Single stones are best used in jewelry, multiple stones should be worn as necklaces, armbands or on key rings.
Source: Healing Crystals and Gemstones by Dr. Flora Peschek-Bohmer and Gisela Schreiber.