Citrine

Citrine is a variety of quartz whose color ranges from a pale yellow to brown. Natural citrines are rare; most commercial citrines are heat-treated amethyst. Citrine contains traces of Fe3+ and is rarely found naturally. The name is derived from Latin citrina which means "yellow". Citrine crystals can form together with amethyst or smoky quartz to form a bi-colored quartz called ametrine.

Natural citrine is pale yellow to pale orange, much lighter than the heat-treated material which is dark orange-brown to reddish-brown. All of the heat-treated material has a red tint, while natural citrine does not. Some amethyst deposits have been found where the amethyst was changed naturally by high temperatures to brown citrine.

Most citrine comes from Brazil, but almost all of the Brazilian material is heat-treated amethyst. Natural citrine can also be found in the Ural Mountains of Russia, in Dauphine, France, and in Madagascar. In Europe, the boom on these yellow to reddish crystal quartzes didn't begin until, in the 1930s, when agate cutters from Idar-Oberstein sent large quantities of citrine back home, along with amethyst and agate, from Brazil and Uruguay. The inexpensive low grade amethyst is heated at high temperatures to produce the popular orange, reddish and sherry colored citrine. Darker colors are considered more valuable, including the medium golden orange and dark sherry-colors.