These pale colors were once considered undesirable, but have recently become popular due to intensive marketing.Green quartz is sometimes incorrectly called green amethyst, which is a misnomer and not an appropriate name for the material, as the proper terminology is prasiolite. Other names for green quartz are vermarine or lime citrine. Amethyst frequently shows color zoning, with the most intense color typically found at the crystal terminations. It is the most prized variety of quartz. One of a gem cutter’s tasks is to make a finished product with even color. Sometimes, only a thin layer of a natural, uncut amethyst is violet colored, or the color is very uneven. The uncut gem may have only a small portion that is suitable for faceting.The color of amethyst has been demonstrated to result from substitution by irradiation of trivalent iron (Fe3+) for silicon in the structure, in the presence of trace elements of large ionic radius, and to a certain extent, the amethyst color can naturally result from displacement of transition elements even if the iron concentration is low. Natural amethyst is dichroic in reddish violet and bluish violet, but when heated, turns yellow-orange, yellow-brown, or dark brownish and may resemble citrine, but loses its dichroism, unlike genuine citrine. When partially heated, amethyst can result in ametrine. Amethyst can fade in tone if overexposed to light sources and can be artificially darkened with adequate irradiation. It does not fluoresce under either short-wave or long-wave UV light. Geographic distribution
Amethyst is found in many locations around the world.
In the Middle Ages, it was considered a symbol of royalty and used to decorate English regalia. In the Old World, amethyst was considered one of the Cardinal gems, in that it was one of the five gemstones considered precious above all others, until large deposits were found in Brazil. Value
Until the 18th century, amethyst was included in the cardinal, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald), but since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value. It is now considered a semiprecious stone.Collectors look for depth of color; possibly with red flashes if cut conventionally. As amethyst is readily available in large structures, the value of the gem is not primarily defined by carat weight. This is different from most gemstones, since the carat weight typically exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed.The highest-grade amethyst (called "Deep Russian") is exceptionally rare. When one is found, its value is dependent on the demand of collectors. The highest-grade sapphires or rubies are still orders of magnitude more expensive than amethyst. Handling and care
The most suitable setting for gem amethyst is a prong or a bezel setting. The channel method must be used with caution.Amethyst has a good hardness, and handling it with proper care will prevent any damage to the stone. Amethyst is sensitive to strong heat and may lose or change its colour when exposed to prolonged heat or light.