Amethyst, Citrine, Ametrine

Amethyst is the most popular member of the quartz family. Its purple color results from natural radiation acting on trace elements of iron in its crystal structure. The color ranges from very light to deep purple to reddish purple. Amethyst crystals form in both veins and geodes. The crystals are usually color zoned being very light at the base and darker toward the tip. Only the tips are used for gem material. Color zoning in cut gems is common.

Citrine is a member of the quartz family with colors ranging from lemon yellow to orange to reddish orange. Natural citrine is rare. Most of the citrine marketed today is actually  amethyst which has been heat treated. When amethyst is heated it changes color from purple to beautiful yellows and oranges. The color saturation of the amethyst prior to heating determines the color of the citrine.

Ametrine is a member of the quartz family and a bi-color variety of amethyst showing both amethyst and citrine colors in the same crystal. This material is mined in only one location, the Bolivias Anahi mine in eastern Bolivia. The rough material is becoming harder to obtain every year. The most valuable ametrine had deep color with sharp separation between colors. Most ametrine is step cut to show the color separation more easily.