Quartz is one of the most abundant minerals in the Earth's crust. It is composed of the elements silicon and oxygen, and in its pure state is colorless. However, small amounts of various impurity atoms can yield a wide range of colors. Amethyst, the most prized gem variety of quartz, is purple. Citrine is the golden-yellow to orange variety of quartz. This fancy cut gem is part amethyst and part citrine, known as ametrine. Even though ametrine is a naturally occurring variety of quartz, most ametrine is artificially created by heat treatment and/or radiation of amethyst. The color zoning in ametrine is due to differing oxidation states of iron inside the crystal. Most ametrine is mined in Bolivia, however there are deposits in Brazil and India.This Bolivian ametrine is natural and a wonderful addition to the National Gem Collection as it beautifully represents state-of-the-art and creative cutting techniques being used today.The Attaway Ametrine, the "Eye of Horus," exhibits faceting combined with one-of-a-kind gemstone carving.