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Chert (/ tʃ ɜːr t /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. [3]
Mozarkite is a form of chert . It is the state rock of Missouri. The name is a portmanteau, formed from Mo (Missouri), zark , and ite (meaning rock). [1] Mozarkite consists essentially of silica (quartz - SiO 2) with varying amounts of chalcedony. It has won distinction as a particular form or variety of chert because of its unique variation of ...
Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start fires. Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones.
Here radiolarian cherts overlie spilites and volcanic rocks. Radiolarites are also found in the nearby Southern Uplands where they are associated with pillow lava. The Scottish radiolarites are followed by deposits in Newfoundland from the Middle and Upper Ordovician. The red Strong Island Chert for instance rests on ophiolites.
The Grassy Knob Chert upper sections are yellowish grey to light olive grey limestone, interbedded with cherty inclusions. Moving lower the amount of chert increases and the color changed to light grey with some olive grey mottling. This formation is generally the same age as the Oriskany Formation of the Appalachian Basin. [2]
Novaculite, also called Arkansas Stone, is a microcrystalline to cryptocrystalline rock type that consists of silica in the form of chert or flint. It is commonly white to grey or black in color, with a specific gravity that ranges from 2.2 to 2.5. It is used in the production of sharpening stones.
Porcellanite from the Czech Republic. Porcellanite or porcelanite, is a hard, dense rock somewhat similar in appearance to unglazed porcelain.It is often an impure variety of chert containing clay and calcareous matter. [1]
These Lagerstätte deposits include the Paleozoic Rhynie Chert and East Kirkton Limestone beds, which record early stages in the evolution of land plants. [11] Most of the color in petrified wood comes from trace metals. Of these, iron is the most important, and it can produce a range of hues depending on its oxidation state.