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Spheroidal or woolsack weathering in granite on Haytor, Dartmoor, England Spheroidal weathering in granite, Estaca de Bares, A Coruña, Galicia, Spain Woolsack weathering in sandstone at the Externsteine rocks, Teutoburg Forest, Germany Corestones near Musina, South Africa that were created by spherodial weathering and exposed by the removal of surrounding saprolite by erosion.
A weathering rind represents the alteration of the outer portion of a rock by exposure to air or near surface groundwater over a period of time. Typically, a weathering rind may be enriched with either iron or manganese (or both), and silica, and oxidized to a yellowish red to reddish color.
The Ashangi Basalts are made of coarse-grained plagioclase minerals, surrounded by a matrix of fine-grained plagioclases and pyroxenes; some iron oxides are also present. [2] Rock sample of extremely porphyritic basalt, collected at Mashih
Iron oxides are derived from mafic igneous rocks and other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks. [15] Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine, pyroxene, and amphibole. [10]: 3
The concretions were created by the precipitation of iron, which was dissolved in groundwater. The iron was originally present as a thin film of iron oxide surrounding sand grains in the Navajo Sandstone. Groundwater containing methane or petroleum from underlying rock beds reacted with the iron oxide, converting it to soluble reduced iron ...
In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation (i.e. water derived from precipitation) with concomitant oxidation and chemical weathering.
Watson Lake in the Granite Dells The Peavine Trail Dells Granite showing spheroidal weathering.. The Granite Dells is a geological feature north of Prescott, Arizona.The Dells consist of exposed bedrock and large boulders of granite that have eroded into an unusual lumpy, rippled appearance.
A significant portion of Rwanda's economy is based on mineral extraction. Rwanda is the foremost producer of tungsten in Africa, producing 70% of Africa's total output. Rwanda is Africa's second highest producer of tin and coltan, accounting for 20% and 30% of the country's output, respectively. Rwanda also produces 9% of the world's tantalum.