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Its color is normally apple-green, but varies from turquoise-like cyan to deep green. The darker varieties of chrysoprase are also referred to as prase . (However, the term prase is also used to describe chlorite -included quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.)
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 ...
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.
Many sandstones are held together by an infinitesimal amount of colloid or cryptocrystalline silica; when freshly dug from the quarry they are soft and easily trimmed, but after exposure to the air for some time they become much harder, as their siliceous cement sets and passes into a rigid condition. Others contain fine scales of kaolin or of ...
A QFL diagram or QFL triangle is a type of ternary diagram that shows compositional data from sandstones and modern sands, point counted using the Gazzi-Dickinson method. The abbreviations used are as follows: Q – quartz; F – feldspar; L – lithic fragments
They are closely related to sandstones in origin, and exhibit many of the same types of sedimentary structures, such as tabular and trough cross-bedding and graded bedding. [ 1 ] [ 2 ] [ 3 ] Fanglomerates are poorly sorted, matrix-rich conglomerates that originated as debris flows on alluvial fans and likely contain the largest accumulations of ...
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Zircon age‐spectra for the sandstones of the Wilcox Group reveal a complex grain assemblage derived from Laramide uplifted crystalline blocks of the central and southern Rocky Mountains, the Cordilleran arc of western North America, and arc‐related extrusive and intrusive igneous rocks of northern Mexico.