Beautiful rock crystal group (45x27 cm) on rotating stand from Jesseville/Arkansas, U.S.A.

Rock crystal is the most common and colourless variety of the mineral quartz (silicon dioxide, SiO2). The name 'rock crystal' is derived from the Greek word "Krustallos,", which means ice. It was believed that rock crystal was given by the gods in the form of ice. Rock crystal was already known during the Mesolithic period. The Alps brought it onto the market during Roman times under the name "petrified ice". Theophrastus called it "Krystallos." Pliny the Elder also mentions it. 'quartz' was introduced in 1529 by Georgius Agricola. The people of the East considered rock crystals to be the stones of patience and perfection. Tibetans use rock crystal to treat wounds. People chose rock crystal as a drinking glass or as part of mediaeval jewellery because they believed these crystals would break or discolour when they came into contact with poison. The chain thus became an amulet that protected the king. Compare the Rudolfin imperial crown and the chain of the Jehovah's Order. Origin: Megnathites, pegmatites, hydrothermal and alpine stone veins, and alluvial deposits. Occurrence: Rock crystal is widespread in nature, but not always in gemstone quality. Historically known sites are India and Sri Lanka (the Tatnaputi area). Iridescent quartz from the Poona area in India and from Myanmar is a rarity. Beautiful crystals come from Kenya and Madagascar, as well as Brazil (Minas Gerais), Goiás, Bahia, and French Guiana. In the USA, rock crystal occurs in pegmatites, including locations in Maine, New York (near Ausburn), North Carolina, Arkansas (Crystal Peak), and California. Of particular significance are occurrences in the Alps. Rock crystals are found in Switzerland (for example, near Urim, where a crystal weighing 135 kg was found in the area of ​​the St. Gotthard and the Grimsel); in Austria, in 1965, a crystal weighing almost 1000 kg was found in a cavity near the Großglockner. Rock crystals are also found in Germany, the Czech Republic, Poland and France. The collections of various museums contain unique cut rock crystals. The Smithsonian Institution in Washington has a cut stone of 7000 ct and a spherical rock crystal with a diameter of 33 cm and a weight of 48.5 kg; this crystal comes from Burma and was cut in China.