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The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
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.
[1] [2] Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sandstone). [3] A pyroclastic rock containing 25–75% volcanic bombs and/or volcanic blocks is called tuff breccia. [4] Tuff composed of sandy volcanic material can be referred to as ...
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 ...
[8] [3] When it is possible to identify the minerals present, trachyandesite is characterized by a high content of sodic plagioclase, typically andesine, and contains at least 10% alkali feldspar. [1] Common mafic accessory minerals are amphibole, biotite or pyroxene. Small amounts of nepheline may be present and apatite is a common accessory ...
The blocks known as the Trilithon (the upper of the two largest courses of stone pictured) in the Temple of Jupiter Baal. The Trilithon (Greek: Τρίλιθον), also called the Three Stones, is a group of three horizontally lying giant stones that form part of the podium of the Temple of Jupiter Baal at Baalbek.
Porphyritic texture in a granite. This is an intrusive porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California. A porphyritic volcanic sand grain, as seen under the petrographic microscope. The large grain in the middle is of a much ...
Andesine occurs in intermediate igneous rocks such as diorite, syenite, and andesite. It characteristically occurs in metamorphic rocks of granulite to amphibolite facies commonly exhibiting antiperthite texture. It also occurs as detrital grains in sedimentary rocks.