Amethyst 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, thus it is suitable for use in jewelry. 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 amethyst can be found in Siberia, Sri Lanka, Brazil 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 (depending on the light source)
Yangtse Incident: The Story of H.M.S. Amethyst refuse to do. Kerans dismisses his demands but is able to manipulate Peng into the release of the Petty Officers; meanwhile, as talks progress he has the ship patched up and its engines restored. After some subtle alterations to the ship's outline to try to disguise her, "Amethyst" slips her cable and heads downriver in the dark following a local merchant ship, which "Amethyst" uses to show the way through the shoals and distract the PLA. When the shore batteries finally notice the frigate escaping downriver, the merchantman receives the brunt of the PLA artillery and catches fire, while "Amethyst"