Smithsonian National Museum of Natural History
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Amethyst

Photograph of a large cushion-cut amethyst (NMNH G9575) from the National Gem Collection
Photo by Chip Clark. Click to zoom.
Catalog Number NMNH G9575-00
Locality Brazil
Weight 109.66 ct

Gift of John W. May in 1982.

Quartz, one of the most abundant minerals in the Earth’s crust, is composed of silicon and oxygen and in its pure state is colorless. When iron replaces some of the silicon atoms, the color is purple. Purple quartz is called amethyst and is the most prized gem variety of quartz. Amethyst is found in a variety of geologic settings, but most commmonly as crystals lining cavities in volcanic rock. The major sources for amethyst are Brazil and Uruguay. This modified rectangular cut amethyst from Brazil is 109.66 carats.

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