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Granite. Granite (/ ˈɡrænɪt / GRAN-it) is a coarse-grained (phaneritic) 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.
The S-type Granya Granite shows the characteristic white feldspars, grey quartz, and black biotite, the highly reflective mineral is muscovite. The S-type Strathbogie Granite crops out in the Strathbogie Ranges of Australia. A hand sample from the Strathbogie Granite has a porphyritic texture with larger crystal of grey quartz, called ...
Rapakivi granite is an igneous intrusive rock and variant of alkali feldspar granite. It is characterized by large, rounded crystals of orthoclase each with a rim of oligoclase (a variety of plagioclase). Common mineral components include hornblende and biotite. The name has come to be used most frequently as a textural term where it implies ...
Graphic texture. Graphic texture is commonly created by exsolution and devitrification and immiscibility processes in igneous rocks. It is called 'graphic' because the exsolved or devitrified minerals form lines and shapes which are reminiscent of writing. Graphic granite is a leucocratic granitic rock consisting of alkali feldspar with ...
Alkali feldspar granite, some varieties of which are called 'red granite', [1] is a felsic igneous rock and a type of granite rich in the mineral potassium feldspar (K-spar). It is a dense rock with a phaneritic texture. The abundance of K-spar gives the rock a predominant pink to reddish hue; peppered with minor amounts of black minerals. [2] [3]
Pikes Peak granite is a 1.08 billion year old Late-Precambrian geologic formation found in the central part of the Front Range of Colorado. It is a coarse-grained pink to light red syenogranite with minor gray monzogranite , and it has a distinctive brick-red appearance where it outcrops.
I-type granite. I-type granites are a category of granites originating from igneous sources, first proposed by Chappell and White (1974). [1] They are recognized by a specific set of mineralogical, geochemical, textural, and isotopic characteristics that indicate, for example, magma hybridization in the deep crust. [2]
Gneiss (/ naɪs / nice) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under pressures anywhere from 2 to 15 kbar, sometimes even more, and temperatures over 300 °C (572 °F).