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Difference between revisions of "Amethyst"
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==Structure== | ==Structure== | ||
Amethyst is a purple variety of [[quartz]] (SiO2) and owes its violet color to irradiation, impurities of iron (Fe3+) and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. Amethyst can fade in tone if overexposed to light sources, and can be artificially darkened with adequate irradiation. It does not fluoresce under either short-wave or long-wave UV light. | Amethyst is a purple variety of [[quartz]] (SiO2) and owes its violet color to irradiation, impurities of iron (Fe3+) and in some cases other transition metals, and the presence of other trace elements, which result in complex [[crystal]] lattice substitutions. Amethyst can fade in tone if overexposed to light sources, and can be artificially darkened with adequate irradiation. It does not fluoresce under either short-wave or long-wave UV light. | ||
Amethyst is a three-dimensional network of tetrahedra where the silicon atoms are in the center and are surrounded by four oxygen atoms located at the vertices of a tetrahedron. This structure is quite rigid and results in quartz's hardness and resistance to weathering. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry. | Amethyst is a three-dimensional network of tetrahedra where the silicon atoms are in the center and are surrounded by four oxygen atoms located at the vertices of a tetrahedron. This structure is quite rigid and results in quartz's hardness and resistance to weathering. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry. | ||
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The highest-grade amethyst (called "Deep Russian") is exceptionally rare. When one is found, its value is dependent on the demand of collectors. The highest-grade sapphires or rubies are still orders of magnitude more expensive than amethyst. | The highest-grade amethyst (called "Deep Russian") is exceptionally rare. When one is found, its value is dependent on the demand of collectors. The highest-grade sapphires or rubies are still orders of magnitude more expensive than amethyst. | ||
== | ==Occurrence== | ||
Amethyst is found in many locations around the world. Between 2000 and 2010, the greatest production was from Marabá and Pau d'Arco, Pará | Amethyst is found in many locations around the world. Between 2000 and 2010, the greatest production was from: | ||
* Brazil: Marabá and Pau d'Arco, Pará; and the Paraná Basin, Rio Grande do Sul | |||
* Bolivia: Sandoval, Santa Cruz | |||
* Uruguay: Artigas | |||
* Zambia: Kalomo | |||
* Canada: Thunder Bay, Ontario | |||
Lesser amounts are found in many other locations in Spain, Argentina, Russia, Afghanistan, South Korea, Mexico, and the United States. | |||
A large geode, or "amethyst-grotto," from near Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany. | A large geode, or "amethyst-grotto," from near Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany. | ||