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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.
The compaction of radiolarites is dependent on their chemical composition and correlates positively with the original SiO 2-content. The compaction factor varies generally between 3.2 and 5, which means that 1 meter of consolidated sediment is equivalent to 3.2 to 5 meters of ooze.
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.
Itabirite, also called banded-quartz hematite or hematite schist, is a foliated, metamorphosed oxide-facies iron formation in which the original chert or jasper bands have been recrystallized into macroscopically distinguishable grains of quartz and the iron is present as thin layers of hematite, magnetite, or martite (pseudomorphs of hematite after magnetite).
Composition [ edit ] Ooids are most commonly composed of calcium carbonate ( calcite or aragonite ), but can be composed of phosphate, clays, chert , dolomite or iron minerals, including hematite .
Banded iron formation from the Barberton Greenstone Belt, South Africa. A typical banded iron formation consists of repeated, thin layers (a few millimeters to a few centimeters in thickness) of silver to black iron oxides, either magnetite (Fe 3 O 4) or hematite (Fe 2 O 3), alternating with bands of iron-poor chert, often red in color, of similar thickness.
Composition of gravel-size clasts they contain; Size range of gravel-size clasts present; The classification method depends on the type and detail of research being conducted. [1] [2] [5] A sedimentary rock composed largely of gravel is first named according to the roundness of the gravel.
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide).The atoms are linked in a continuous framework of SiO 4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO 2.