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Smithsonian National Museum of Natural History

Quartz (var. ametrine)

Pentagon-cut purple/brown yellow quartz (var. ametrine) weighing 91.93 ct.
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Catalog Number NMNH G10694-00
Locality Brazil
Weight 91.93 ct

Purchased with funds from the Tiffany & Co. Foundation in 2011.

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. The gem pictured here is part amethyst and part citrine, known in the trade as ametrine. The color zoning in ametrine is due to differing oxidation states of iron inside the crystal. The most significant source of ametrine is from the Anahi Mine in eastern Bolivia. However, there are deposits in Brazil and India. Even though ametrine is a naturally occurring variety of quartz, most ametrine is artificially created by heat treatment and/or radiation of amethyst. The Anahi Mine is the only mine known where commercial quantities of natural ametrine are found. The pentagon-shaped ametrine weighs 91.93cts and was faceted by Jeff Gurecky. It displays the purple violet to golden yellow bi-color of gem ametrine and was acquired with the Tiffany & Co. Foundation endowment in 2011. Photo courtesy of Paul Merkel.


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