Search results
Results from the WOW.Com Content Network
Greywacke or graywacke (German grauwacke, signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness (6–7 on Mohs scale), dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or sand-size lithic fragments set in a compact, clay-fine matrix.
Ermelo Sandstone, Mpumalanga province, near der Farm de Roodepoort Matatiele Sandstone , KwaZulu-Natal province, near Matatiele Naboomspruit (also Golden Dawn or Golden Stone ) Limpopo province, around Warmbaths
Arkose – Type of sandstone containing at least 25% feldspar; Banded iron formation – Layered iron-rich sedimentary rock; Breccia – Rock composed of angular fragments; Calcarenite – Type of limestone that is composed predominantly of sand-size grains; Chalk – Soft carbonate rock
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 ...
The grey and white crystals are quartz and (limited) feldspar. Metamorphism is the transformation of existing rock (the protolith ) to rock with a different mineral composition or texture . Metamorphism takes place at temperatures in excess of 150 °C (300 °F), and often also at elevated pressure or in the presence of chemically active fluids ...
Phyllite Photomicrograph of thin section of phyllite (in cross polarised light) Fractured Duke stone showing phyllitic texture Phyllite. Phyllite (/ ˈ f ɪ l aɪ t / FIL-yte) is a type of foliated metamorphic rock formed from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation. [1]
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000 bar ) or more, causing profound physical or chemical changes.
The Temple Butte strata filling these paleovalleys consist of interbedded mudstone, sandstone, dolomite, and conglomerate – that vary in color from purple, reddish-purple, to light gray. Typically, the paleovalley-fill consists of a distinct pale, reddish purple dolomite or sandy dolomite.