Amethyst is not primarily defined by carat weight; this is different to most gemstones where the carat weight 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 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). Amethyst Amethyst is a violet variety of quartz. The name comes from the Koine Greek ἀμέθυστος "amethystos" from
Amethyst gasfield Amethyst gasfield Amethyst is a natural gas field in the Southern North Sea, about east of the Yorkshire coast. Gas lies in a Permian sandstone reservoir around below the seabed. The gasfield is operated by BP. The gasfield was discovered in 1972 and it was named after HMS "Amethyst". Between 1972 and 1985 a number of appraisal wells were drilled. The field development started in 1988 and the first gas was produced in 1991. Originally, the field was owned by BP, Enterprise Oil, British Gas, ARCO, Murphy Oil, Amerada Hess, and FINA. In 1997, BP acquired the interest of Enterprise