Amethyst

Amethyst is a violet variety of quartz  often used in Jewellery . The name comes from the Ancient Greek  ,a reference to the belief that the stone protected its owner from drunkness  Greek  and Romans wore amethyst and made drinking  vessels of it in the belief that it would prevent intoxication.

Nature 

Amethyst is a purple variety of quartz (SiO₂) and owes its violet color to irradiation,iron  impurities (in some cases in conjunction with transition  element impurities), and the presence of trace elements, which result in complex crystal lattice substitutions. The hardness of the mineral is the same as quartz on Mohs Scale it is -7, thus it is suitable for use in jewelry.

Color -

Amethyst occurs in primary hues from a light pinkish violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue. The best varieties of Amethysts can be found in Srilanka , Brazil, Africa,Siberia and the far East. The ideal grade is called "Deep Siberian" and has a primary purple hue of around 75–80%, with 15–20% blue and (depend on the light source) red secondary hues.

 Amethyst Belongs to-

Amethyst is produced in abundance from the state of Minas Geris in Brazil where it occurs in large deodes within volcanic rocks . Many of the hollow agates of southwestern Brazil and Urugauay contain a crop of amethyst crystals in the interior. 

 It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Much fine amethyst comes from Russai, especially from near Mursinka in the Ekaterinburg district, where it occurs in drsy cavities in granitic rocks. Many localities in south India   yield amethyst. One of the largest global amethyst producers is Zambia in southern Africa with an annual production of about 1000 tonnes.

Value -

 Up until the 18th century, amethyst was included in the cardina, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald). However, since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value.

Collectors look for depth of color, possibly with red flashes if cut conventionally.

 The highest grade amethyst (called "Deep Russian") is exceptionally rare and therefore, when one is found, its value is dependent on the demand of collectors. It is, however, still orders of magnitude lower than the highest grade sapphires or rubies (padparadscha sapphire or "pigeon's blood" ruby).