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
SS Empire Amethyst distress call from the American SS "Delvalla" which had been torpedoed by "U-154" and was sinking. "Prince Henry" headed for the reported position of the "Delvalla" and a Catalina aircraft was despatched. The survivors were taken aboard "Prince Henry". "U-154" spotted "Empire Amethyst" again at 11:42 hrs; she was again under escort by "Prince Henry" but at 16:00 hrs the escort had been lost. As he was short of torpedoes, Kapitän Kölle decided to attack from the surface. The chase began at 20:00 hrs with "Empire Amethyst" zig-zagging but generally following a heading of 110° towards Trinidad. "Empire Amethyst" managed