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Onyx
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Minas Gerais, Brazil
© Rob Lavinsky
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| System: | Trigonal | Colour: | Black and white | |||||
| Lustre: | Waxy | Hardness: | 6½ - 7 | |||||
A variety of Agate
In correct usage, the name refers to a black and white banded variety of Agate, or sometimes a monochromatic agate with dark and light bands (brown and white for example) - but traditionally the name was reserved for black and white banded agate, and brown varieties named Sardonyx.
In recent times the name has become confused with other banded materials, in particular banded calcite formed in cave systems such as the material found in Mexico and Pakistan and often carved, in fact the majority of carved material (such as book-ends, chess-sets, etc) that are available today are made from this carbonate rock. This is a carbonate material and is not true Onyx. Other names have been used over time for this material, such as "Mexican Onyx" and "onyx-marble". Careless use of these names has resulted in the term 'Onyx' being incorrectly applied to a variety of banded materials that are not covered by the original definition of the name.
Visit gemdat.org for gemological information about Onyx. Currently in public beta-test.
In correct usage, the name refers to a black and white banded variety of Agate, or sometimes a monochromatic agate with dark and light bands (brown and white for example) - but traditionally the name was reserved for black and white banded agate, and brown varieties named Sardonyx.
In recent times the name has become confused with other banded materials, in particular banded calcite formed in cave systems such as the material found in Mexico and Pakistan and often carved, in fact the majority of carved material (such as book-ends, chess-sets, etc) that are available today are made from this carbonate rock. This is a carbonate material and is not true Onyx. Other names have been used over time for this material, such as "Mexican Onyx" and "onyx-marble". Careless use of these names has resulted in the term 'Onyx' being incorrectly applied to a variety of banded materials that are not covered by the original definition of the name.
Visit gemdat.org for gemological information about Onyx. Currently in public beta-test.
Classification of Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
| mindat.org URL: | http://www.mindat.org/min-2999.html Please feel free to link to this page. | ||||||||||||||||||||||||||||||||||||||||||||||
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Physical Properties of Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
| Lustre: | Waxy | ||||||||||||||||||||||||||||||||||||||||||||||
| Diaphaneity (Transparency): | Translucent, Opaque | ||||||||||||||||||||||||||||||||||||||||||||||
| Comment: | Vitreous when polished | ||||||||||||||||||||||||||||||||||||||||||||||
| Colour: | Black and white | ||||||||||||||||||||||||||||||||||||||||||||||
| Comment: | often produced by dying agates | ||||||||||||||||||||||||||||||||||||||||||||||
| Streak: | white | ||||||||||||||||||||||||||||||||||||||||||||||
| Hardness (Mohs): | 6½ - 7 | ||||||||||||||||||||||||||||||||||||||||||||||
| Fracture: | Conchoidal | ||||||||||||||||||||||||||||||||||||||||||||||
| Density (measured): | 2.6 - 2.65 g/cm3 | ||||||||||||||||||||||||||||||||||||||||||||||
| Comment: | varies with amount and type of impurities | ||||||||||||||||||||||||||||||||||||||||||||||
Crystallography of Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
| Crystal System: | Trigonal | ||||||||||||||||||||||||||||||||||||||||||||||
Chemical Properties of Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
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| Essential elements: | O, Si | ||||||||||||||||||||||||||||||||||||||||||||||
| All elements listed in formula: | O, Si | ||||||||||||||||||||||||||||||||||||||||||||||
Other Names for Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
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Other Information | |||||||||||||||||||||||||||||||||||||||||||||||
| Health Warning: | No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care. | ||||||||||||||||||||||||||||||||||||||||||||||
Internet Links for Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
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Localities for Onyx | |||||||||||||||||||||||||||||||||||||||||||||||
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The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the
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The symbol next to localities in the list
can be used to jump to that position on the map.
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