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
HMS Amethyst (F116) took place in the North Atlantic, south of Waterford and resulted in the loss of all 49 of the U-boat's crew. During the war the "Amethyst" was credited, along with the sloops , , , and frigate , with sinking the in the North Channel on 16 January 1945. The British Admiralty withdrew this credit in a post-war reassessment. On 20 April 1949, "Amethyst" was on her way from Shanghai to Nanking (now Nanjing) when she was fired upon by the People's Liberation Army, thus starting the Amethyst Incident. "Amethyst" was trapped in China until 30 July 1949 when she