Rock crystal (from Greek kruos and krustallos, ‘frost’ or ‘ice’), Earth’s purest form of quartz, is found worldwide and is the second most abundant mineral after feldspar. This colorless, transparent to translucent silicon oxide (SiO2) quartz, also known as pure or clear quartz, forms hexagonal prisms often ending in a pyramid. It measures 7 on the Mohs hardness scale.
The ancients believed pure quartz was superhard, petrified ice and that the gods lived in palaces of rock crystal; knapped tools and weapons such as arrowheads were made from it. The emperor Nero drank his wine from a rock crystal goblet, as this mineral was supposed to quench thirst, and wealthy Roman ladies carried it in their hands during hot weather because they thought it had cooling properties. Pure quartz is the traditional material used to make seers’ crystal balls; 11th century crusaders brought these objects back from the Holy Land, believing they possessed magical powers of divination and healing. Subsequently, clear quartz became popular in medieval Europe as a treatment for a slew of conditions including dysentery, colic, fever, pain, gout and kidney disease. For Native Americans, rock crystal is a good luck stone to be placed in a newborn baby’s cradle. Rock crystal is a symbol of purity, patience and perseverance for the Japanese, who call it tama, the Perfect Jewel. It is thought to open the heart and mind to higher guidance, and is used in the quest to achieve enlightenment.
Rock crystal is considered a semi-precious stone and can be left raw, shaped or tumbled smooth in jewelry, touchstones, carvings and meditation aids, or as decorative clusters or geodes. The genuine stone also had industrial applications and was used in timepieces, but most modern quartz movement watches and electronics now employ synthetic rock crystal.