How does bedded chert form?
Deep water upwellings bring nutrient rich waters to the surface resulting in algal blooms, population explosions of microscopic organisms, many of whom produce silicious skeletons which settle to the bottom and recrystallize to form form thick bedded chert.
Does chert have bedding?
Bedded chert, also known as ribbon chert, takes the form of thinly bedded layers (a few centimeters to a meter in thickness) of nearly pure chert separated by very thin layers of silica-rich shale. It is usually black to green in color, and the full sequence of beds may be several hundred meters thick.
How is siliceous ooze transformed into bedded chert?
Many bedded cherts are composed almost entirely of the remains of silica-secreting organisms like diatoms and radiolarians. Such deposits are produced by compacting and recrystallizing the organically produced siliceous ooze deposits that accumulate on the present-day abyssal ocean floor.
What is the classification of chert?
Chert is a fine-grained sedimentary rock composed of quartz (SiO2) that is microcrystalline or cryptocrystalline quartz. It is usually organic rock but also occur inorganically as a chemical precipitate or a diagenetic replacement. It occurs as nodules, concretionary masses, and as layered deposits.
Is chert a crystal?
Chert is very fine-grained, so it does not occur as the 6-sided, prismatic crystals typical of such coarsely crystalline varieties of quartz as rock crystal, amethyst, smoky quartz and citrine. It does, however, have the mineral properties of quartz.
How common is chert?
Chert is widespread, but not widely known by the public as a distinct rock type.
What is chert good for?
Chert is of interest to rock collectors, gemologists, geologists, and knappers (those who produce stone tools like those of Native Americans), and it is used in the production of sharpening stones and abrasive products. But one of the most common uses of chert is as part of the aggregate in concrete products.
What color is chert?
Flint is gray to black and nearly opaque (translucent brown in thin splinters) because of included carbonaceous matter. Opaque, dull, whitish to pale-brown or gray specimens are simply called chert; the light colour and opacity are caused by abundant, extremely minute inclusions of water or air.
Where is chert found?
Chert layers are commonly found in eastern Kansas, occurring as irregular beds or rounded nodules within limestone formations. Chert is harder than limestone and is thus more resistant to erosion. The chert-topped hills in the Flint Hills resulted from this uneven erosion of the landscape.
Where is chert most abundant?
Erosion of chert beds or chert-bearing limestone produces chert pebbles, which are abundant in river and beach gravel. Most chert and flint has formed by replacement of the enclosing carbonate sediment after burial beneath the seafloor.
What does chert feel like?
Hardness – hard. Colour – all colours, dependent on impurities present when precipitated. Clasts – none. Other features – smooth to touch, glassy, exhibits conchoidal fracture.
What kind of structure is a bedded chert?
Chert of brittle, close-jointed, rhythmically layered character found over large areas in thick deposits, the usually even-bedded layers separated by partings of dark siliceous shale or by siderite layers.
What makes up a bed of chert and Flint?
Chert and flint. Bedded chert, also referred to as ribbon chert, is made up of layers of chert interbedded with thin layers of shale. Many bedded cherts are made up of the remains of siliceous organisms such as diatoms, radiolarians, or sponge spicules.
What kind of rock is a chert rock?
Chert is dense and hard sedimentary rock, consisting mostly microcrystalline quartz. These rocks may frequently occur together. Chert is either nodular or forms layers (bedded chert).
Where does chert come from in the ocean?
The third setting that gives rise to chert is in deep-sea basins, where the microscopic shells of siliceous plankton, mostly diatoms, accumulate from the surface waters above. This kind of chert is bedded, like many other sedimentary rocks.