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Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene.The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite.
The quartz crystals exist in a fine-grained matrix, usually of micro-crystalline or felsitic structure. In specimens, the quartz appears as small rounded, clear, greyish, vitreous blebs, which are crystals, double hexagonal pyramids, with their edges and corners rounded by resorption or corrosion.
Hornblende diorite from the Henry Mountains, Utah, US. Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss, and schist. It crystallizes in preference to pyroxene minerals from cooler magma that is richer in silica and water. [13]
"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.
Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux , meaning "light", and generally implies radiance, gloss, or brilliance.
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Quartz diorite is an igneous, plutonic rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase (typically oligoclase or andesine ) with 10% or less potassium feldspar.
Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. [3] Along with basalts, andesites are a component of the Martian crust.