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The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt, andesite, and rhyolite. Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass ...
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.
Granodiorite (/ ˌ ɡ r æ n oʊ ˈ d aɪ. ə r aɪ t, ˌ ɡ r æ n ə ˈ-/ GRAN-oh-DY-ə-ryte, GRAN-ə-) [1] [2] is a coarse-grained intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from granite to diorite ...
A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm. Adakite – Volcanic rock type; Andesite – Type of volcanic rock; Alkali feldspar granite – Type of igneous rock rich in alkali feldspar; Anorthosite – Mafic intrusive igneous rock composed predominantly of plagioclase
Tonalite is an igneous, plutonic rock, of felsic composition, with phaneritic (coarse-grained) texture. Feldspar is present as plagioclase (typically oligoclase or andesine ) with alkali feldspar making up less than 10% of the total feldspar content.
Andesite (/ ˈ æ n d ə z aɪ t /) [1] is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. [2]
A subvolcanic rock, also known as a hypabyssal rock, is an intrusive igneous rock that is emplaced at depths less than 2 km (1.2 mi) within the crust, and has intermediate grain size and often porphyritic texture between that of volcanic rocks, which are extrusive igneous rocks, and plutonic rocks, which form much deeper in the ground. [1]
The texture is called granophyric. The texture can be similar to micrographic texture and to the coarser graphic intergrowths of quartz and alkali feldspar common in pegmatite . These textures document simultaneous crystallization of quartz and feldspar from a silicate melt at the eutectic point, perhaps in the presence of a water-rich phase.