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 (1903) was begun. The squadron returned to the Port of Bahia without success. A further attempt to find "Möwe" was made on 24 January when "Amethyst" was joined by , but this was also unsuccessful. Patrols to search for German surface raiders were also conducted in April and May 1917. After a long stay in Rio de Janeiro, "Amethyst" sailed on 5 April 1918, patrolling down the coast inspecting vessels and arriving in Montevideo on 10 March. On 31 May 1918 "Amethyst" left Bahia, Brazil to return to Devonport. On the way home, she met off the coast of Sierra Leone