Definition
Mohs scale hardness 7 and less
Amethyst is a purple variation of quartz (SiO2). Its violet hue is the consequence of complicated crystal lattice substitutions brought on by irradiation, iron and, in certain circumstances, other transition metal impurities, as well as the presence of other trace elements. The mineral is appropriate for use in jewelry since its hardness is the same as quartz's.
Amethyst was once counted among the cardinal, or most precious, gemstones, along with diamond, sapphire, ruby, and emerald, but this has changed significantly since the discovery of large reserves in countries like Brazil. Nowadays, it is regarded as a semiprecious stone.
Collectors want for color depth, potentially with red flashes on traditionally cut pieces. Although amethyst is frequently found in huge structures, its value is not largely determined by its carat weight. This is distinct from most gemstones since the value of a gemstone normally grows exponentially as the carat weight increases. The hue shown is the main determinant of amethyst value.
Varieties of Quartz
Sardonyx
The two most popular semiprecious stones formerly used were sard and sardonyx, translucent, light- to dark-brown variants of the silica mineral chalcedony. Jewelry with engravings has been made out of sard and its close related carnelian for millennia. Sardion, which contained both sard and carnelian until the Middle Ages, was the original name for sard (from Sardis, the ancient capital of Lydia). It is a silica mineral's earliest known name outside of crystal. Sri Lanka's Ratnapura is one area well known for producing sard. Sardonyx, which used to be more valuable than gold, silver, or sapphire, is a band made of sard and white chalcedony. Intaglios and cameos frequently use sardonyx. It has quartz-like characteristics.
Origins
Amethyst may be discovered all around the planet. The Paraná Basin, Rio Grande do Sul, Brazil's Marabá and Pau d'Arco, Bolivia's Sandoval, Uruguay's Artigas, Zambia's Kalomo, and Canada's Thunder Bay produced the most between 2000 and 2010. Several other places in Africa, Brazil, Spain, Argentina, Russia, Afghanistan, South Korea, Mexico, and the United States have lower concentrations. In the Brazilian state of Rio Grande do Sul, where it is found in huge geodes beneath volcanic rocks, amethyst is produced in great quantities. The inside of many of the hollow agates found in southeastern Brazil and Uruguay is covered in amethyst crystals. Large global producers include Artigas, Uruguay, and the nearby state of Rio Grande do Sul in Brazil. Minas Gerais and Bahia also mine certain minerals, albeit to a smaller extent.
South Korea is another country that mines amethyst. While historically significant, the massive opencast amethyst vein in Maissau, Lower Austria, is no longer counted among major producers. A significant amount of beautiful amethyst originates in Russia, particularly in the region of Ekaterinburg close to Mursinka, where it is found in drusy cavities in granitic rocks. Several places in south India used to mine amethyst, however these places are no longer important producers. With an annual production of about 1000 tons, Zambia in southern Africa is one of the world's major amethyst producers.
A synthesis technique called hydrothermal growth, which produces the crystals within a high-pressure autoclave, is used to create synthetic (laboratory-grown) amethyst.The process of treating amethyst involves bombarding transparent quartz (rock crystal) with gamma, X, or electron beams after doping it with ferric impurities beforehand. The effects of radiation are somewhat counteracted by heat exposure, and amethyst often becomes yellow or even green. Many pieces of citrine, cairngorm, or yellow quartz jewelry are allegedly just "burned amethyst."