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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

Lustre:Waxy, Dull
Diaphaneity (Transparency):Translucent, Opaque
Colour:Gray, white; black, brown and other colors due to staining
Streak:White or lightly colored
Hardness (Mohs):6½ - 7
Cleavage:None Observed
Fracture:Splintery, Conchoidal, Sub-Conchoidal

Other Names for Chert

Other Languages:
Simplified Chinese:硅质岩

Other Information

Health Warning:Like all quartz, breathing in fine particles for a prolonged period will produce silicosis.

Internet Links for Chert

Search Engines:
  • Look for Chert on Google
  • Look for Chert images on Google
  • Mineral Dealers:
  • Buy RARE Minerals from Rocks of Africa
  • rare and unusual minerals mainly crystallized
  • Fine Minerals from Weinrich Minerals, Inc.
  • SpiriferMinerals.com - high quality low prices
  • Buy from McDougall Minerals
  • DAKOTA MATRIX offers Cabinet and Rare Species from Worldwide Localities.
  • Fine minerals from bisbeeborn.com
  • The Arkenstone - Fine Minerals
  • Chert specimens for sale - minfind.com
  • Rare and Unusual minerals at Mineralogical Research Company
  • Fine and rare minerals from mintreasure.com
  • Fabre Minerals - search for Chert specimens
  • Localities for Chert

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