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Owingsville, Bath Co., Kentucky, USA
© 2006 Peter Cristofono
|Colour:||Gray, white; black, ...||Hardness:||6½ - 7|
|Name:||"Chert, perhaps originally chirt, is believed to be a local English term that was taken into geological use. It may be of onomatopoeic origin. The name chert may be of more recent origin than flint, and unlike flint, is not found in literary usage. It was well established in meaning in 1679 ..." (Frondel, C., 1962, The System of Mineralogy, v. 3, John Wiley & Sons, p. 223.)|
A tough, dense rock composed of quartz and few other impurities. The quartz occurs as randomly interlocked, microscopic quartz grains (microquartz) or microscopic grains of fibrous chalcedony.
Chert forms layers and nodules, but also large beds in sedimentary and metamorphic rocks, occurs in epithermal veins, by direct deposition around submarine hydrothermal vents and may form as a product of silicification of biogenic or volcanogenic sediments. Chert of sedimentary origin often contains fossils.
The term "chert" is used for rocks mostly composed of quartz, siliceous precursor rocks of comparable texture are sometimes also called chert, but with the addition of the dominant silica phase, like "opaline chert".
Classification of Chert
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Physical Properties of Chert
|Diaphaneity (Transparency):||Translucent, Opaque|
|Colour:||Gray, white; black, brown and other colors due to staining|
|Streak:||White or lightly colored|
|Hardness (Mohs):||6½ - 7|
|Fracture:||Splintery, Conchoidal, Sub-Conchoidal|
Other Names for Chert
|Health Warning:||Like all quartz, breathing in fine particles for a prolonged period will produce silicosis.|
Internet Links for Chert
Localities for Chert
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.