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Granite (/ ˈ ɡ r æ n ɪ t / GRAN-it) is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Close-up of granite (an intrusive igneous rock) Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body. The classification of the many types of igneous rocks can provide important information about the conditions under which they formed.
Aplite – Fine-grained intrusive igneous rock type similar to granite Basalt – Magnesium- and iron-rich extrusive igneous rock ʻAʻā – Molten rock expelled by a volcano during an eruption Pages displaying short descriptions of redirect targets – Basaltic lava with a crumpled appearance
Examples of phaneritic igneous rocks are gabbro, diorite, and granite. Porphyritic textures develop when conditions during the cooling of magma change relatively quickly. The earlier formed minerals will have formed slowly and remain as large crystals, whereas, sudden cooling causes the rapid crystallization of the remainder of the melt into a ...
A fine-grained, mafic igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar. basement rock The thick foundation of ancient, and oldest metamorphic and igneous rock that forms the crust of continents, often in the form of granite. basic rock Igneous rock with low silica ...
Acidic rock or acid rock refers to the chemical composition of igneous rocks that has 63% wt% SiO 2 content. [1] Rocks described as acidic usually contain more than 20% of free quartz. [2] Typical acidic rocks are granite or rhyolite. The term is used in chemical classification of igneous rock based on the content of silica (SiO 2).
These rocks are largely igneous in origin, mixed with metamorphosed marble, quartzite and mica schist with later intrusions of basaltic dikes and granite magma. [ 21 ] The Morton Gneiss is an Archean-age gneiss exposed in the Minnesota River Valley of southwestern Minnesota , United States.
Granite rock hand-sized sample. A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. [1] Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites. [2]