Rock crystal from Nigeria, "always fits" 6mm bullet bracelet.

Rock crystal is the colorless and most common variant of the mineral quartz (silicon dioxide, SiO2). The name "rock crystal" is derived from the Greek word "Krustallos" which means ice. Rock crystal was believed to be ice shaped by the gods. Rock crystal was already known at the time of the Mesolithic. During Roman times it was marketed from the Alps under the name "petrified ice". Theofratus called it "krystallos". Pliny the Elder also mentions it. The name "quartz" was introduced by Georgius Agricola in 1529. The peoples of the East regarded rock crystal as a stone of patience and perfection. Tibetans use rock crystal to treat wounds. The choice of rock crystal as a drinking glass or as part of medieval jewelry can are attributed to the belief that these crystals would break or discolor when in contact with poison. Thus the chain became an amulet protecting the king. Compare the Rudolfine imperial crown and the chain of the Jehovah order. Origin: Megnatites, pegmatites, hydrothermal and alpine stone veins, alluvial deposits. Appearance: Rock crystal is widespread in nature, but not always in gem quality. Historically known sites are India and Sri Lanka (Tatnaputi area). Iridescent quartz from the Poona region of India and from Myanmar is rare, beautiful crystals come from Kenya and Madagascar, also from Brazil (Minas Gerais), Goisas, Bahia and French Guiana. In the US, rock crystal occurs in pegmatites, including in Maine (at Ausburn, New York, North Carolina, Arkansas (Crystal Peak) and California. Of special significance are occurrences in the Alps. Rock crystals are found in Switzerland (for example at Urim where a 135 kg crystal has been found in the area of ​​St. Gotthard and Grimsel), in Austria (in 1965 a crystal of almost 1000 kg was found in a cavity near the Großglockner). , Poland and France. In the collections of several museums there are unique cut rock crystals. The Smithsonian Institution Washington has a cut stone of 7000 ct and a sphere rock crystal with a diameter of 33 cm and a weight of 48.5 kg. Burma and cut in China.