Typical felsic rocks are dacite and rhyolite. Felsic magmas are the most viscous because of their high silica content. Intermediate rocks, such as andesite, fall between the mafic and felsic classifications.
Igneous Rocks: textures and compositionsFelsicMaficCoarse- grainedgranitegabbroFine- grainedrhyolitebasaltMineralsquartz, K-feldspar, amphibole, muscovite, biotiteolivine, pyroxene, Ca-feldspar (plagioclase)Feb 23, 2005
Intrusive Rocks Plutonic and hypabyssal felsic rocks may occur as batholiths, plutons, stocks, laccoliths, dikes, sills and plugs. The largest are granitoid batholiths, which are composite intrusions composed of many individual plutons and associated with active continental margins (see Granite and Granitoids).
graniteFor example, a felsic intrusive rock is called granite, whereas a felsic extrusive rock is called rhyolite. Granite and rhyolite have the same mineral composition, but their grain size gives each a distinct appearance.
Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.
For example, a coarse-grained, felsic igneous rock is not only a granite, it is an intrusive igneous rock that formed from slow cooling and crystallization of a body of magma within the earth's crust.
The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.Oct 10, 2019
BasaltBasalt and gabbro are the extrusive and intrusive names for mafic igneous rocks, and peridotite is ultramafic, with komatiite as the fine-grained extrusive equivalent.Feb 14, 2021
Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth's surface. These are the rocks that form at erupting volcanoes and oozing fissures.
extrusive igneous rocks Such openings are called vesicles, and the rocks in which they occur are said to be vesicular.
Igneous rocks may be divided into two categories. Intrusive or plutonic rocks crystallize from magma beneath the earth's surface. Extrusive or volcanic rocks crystallize from lava at the earth's surface. ... In addition to texture, igneous rocks may are classified according to their chemical composition.
extrusive igneous rockrhyolite, extrusive igneous rock that is the volcanic equivalent of granite. Most rhyolites are porphyritic, indicating that crystallization began prior to extrusion.