Amethyst 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. Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglio engraved gems. The largest Ancient Egyptian amethyst mines are located at Wadi el-Hudi and those mines may be the
HMS Amethyst (1799) Guadaloupe, and his suite. On 30 July, "Amethyst" and two other frigates, and , sailed from Plymouth for the Isle of wight. There they were to pick up Dutch troops that they were to return to Holland. On 10 September "Amethyst" captured the French lugger "Alert", and recaptured a ship. In October 1801 Captain Charles Taylor took command of "Amethyst", only to be replaced in the next month by Captain Henry Glynn, for the North Sea. During the Peace of Amiens, "Amethyst" sailed on anti-smuggling patrols off the coast of Scotland under the command of Captain Alexander Campbell. During the