Chert
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Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide. Chert is characteristically of biological origin, but may
A hand sized sample of chert
Chert (dark bands) in the Devonian Corriganville-New Creek limestone, Everett, Pennsylvania
Folded beds of chert comprising the Late Permian to Jurassic-aged Liminangcong Formation at Busuanga, Palawan, Philippines
Chert nodule within soft limestone at Akçakoca, Turkey
Radiolarite
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Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is also
Outcrop of Franciscan radiolarian chert in San Francisco, California
Radiolarian chert outcrop near Cambria, California. Individual beds range from about 2 to 5 cm thick
Radiolarite (Jurassic) from the Alps.
Whetstone limestone from the Ammergau Alps, Upper Bavaria with round radiolarian remains (thin section). The abrasive effect of the whetstones results from the even distribution of the hard radiolarian skeletons in the soft limestone matrix.