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Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula Cu Al 6 (PO 4) 4 8 ·4H 2 O.It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.
This chart is similar to those used in igneous petrology. When plotted correctly, this model of analysis creates a meaningful quantitative classification of sandstones. [24] A sandstone provenance chart is typically based on a QFL chart but allows geologists to visually interpret the different types of places from which sandstones can originate.
Steenpan (also Flatpan or Klippan), Free State province, near Wolvehoek; Table Mountain Sandstone Western Cape province, various quarry sites; numerous types, some without trade names, from the Karoo Supergroup in many quarries near Graaff-Reinet, Cradock, Queenstown, Aliwal North, Burgersdorp and Sterkstroom; Těšínský sandstone quarry ...
Lithic sandstones can have a speckled (salt and pepper) or gray color, and are usually associated with one specific type of lithic fragment (i.e., igneous, sedimentary, or metamorphic). [ 1 ] Tectonically, lithic sandstones often form in a wide variety sedimentary depositional environments (including fluvial , deltaic , and alluvial sediments ...
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The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. [7]
Nugget Sandstone near Red Fleet Reservoir, Uintah County, Utah. Uniform grain size and these large cross-stratification are indicative of an ancient sand dune.
Table Mountain seen from Signal Hill, across the Cape Town city bowl. The portion of the mountain made up of Table Mountain Sandstone is indicated on the right. [1] It is this mountain that has given its name to the geological structure that occurs in the mountains throughout the Western Cape Schematic diagram of an approximate 100 km west-east (left to right) geological cross-section through ...