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Graphic granite is a leucocratic granitic rock consisting of alkali feldspar with exsolved quartz typically forming a distinctive repetitive pattern sometimes resembling cuneiform writing. Experiments have shown that graphic granite texture is derived from large single crystals of quartz and feldspar interleaving to create the cuneiform illusion.
Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. The six main types of textures are phaneritic, aphanitic, porphyritic, glassy, pyroclastic, and pegmatitic.
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 ...
Granophyric textures can be found in S-type granites, particularly leucocratic ones. In porphyritic S-type granites, phenocrysts are commonly feldspars, but can also be quartz, and in rare cases, such as the Strathbogie Granite, cordierite. Figure 7 shows an example of granophyric texture in the Strathbogie Granite. The mineral quartz (light ...
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]
Aplite dyke cutting Sentinel granodiorite on Sentinel Dome Aplite, showing fine-grained texture Aplite ( / ˈ æ p l aɪ t / ) is an intrusive igneous rock that has a granitic composition. Aplites are fine-grained to aphanitic (without grains visible to the naked eye) and may consist of only quartz and feldspar or the term may refer to any ...
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Granophyre (/ ˈ ɡ r æ n ə f aɪər / GRAN-ə-fire; [1] [2] from granite and porphyry) is a subvolcanic rock that contains quartz and alkali feldspar in characteristic angular intergrowths such as those in the accompanying image. The texture is called granophyric.