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Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon. [16] Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins.
Ilmenite is a titanium-iron oxide mineral with the idealized formula FeTiO 3.It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium [5] and the main source of titanium dioxide, which is used in paints, printing inks, [6] fabrics, plastics, paper, sunscreen, food and cosmetics.
Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs with almandine garnet, micas, kyanite; as well as albite, biotite, and sillimanite in gneiss and schist of regional metamorphic rocks. [7] It is the official state mineral of the U.S. state of Georgia and is also to be found in the Lepontine Alps in Switzerland.
"Imperial Porphyry" from the Red Sea Mountains of Egypt A waterworn cobble of porphyry Rhyolite porphyry from Colorado; scale bar in lower left is 1 cm (0.39 in). Porphyry (/ ˈ p ɔːr f ə r i / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass.
Greenschist is defined by the presence of the minerals chlorite, epidote, or actinolite, which give the rock its green color.Greenschists also have pronounced schistosity. [3]
Because every mineral is stable only within certain limits, the presence of certain minerals in metamorphic rocks indicates the approximate temperatures and pressures at which the rock underwent metamorphism. These minerals are known as index minerals. Examples include sillimanite, kyanite, staurolite, andalusite, and some garnet. [15] Other ...
Hematite (/ ˈ h iː m ə ˌ t aɪ t, ˈ h ɛ m ə-/), also spelled as haematite, is a common iron oxide compound with the formula, Fe 2 O 3 and is widely found in rocks and soils. [6] Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust. Kyanite is also known as disthene or cyanite. [5]
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