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Mineral symbols (text abbreviations) are used to abbreviate mineral groups, subgroups, and species, just as lettered symbols are used for the chemical elements. The first set of commonly used mineral symbols was published in 1983 and covered the common rock-forming minerals using 192 two- or three-lettered symbols. [ 1 ]
Granite is typical of a larger family of granitic rocks, or granitoids, that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification ), with true granite representing granitic rocks rich in ...
A-type granite is a particular category of the S-I-A-M or 'alphabet' system which classifies granitoids and granitic rock by their photoliths or source. [ 1 ] [ 2 ] The 'A' stands for Anorogenic or Anhydrous , as these granites are characterized by low water content and a lack of orogenic or transitional tectonic fabric. [ 3 ]
The name has come to be used most frequently as a textural term where it implies plagioclase rims around orthoclase in plutonic (intrusive) rocks. Rapakivi is a Finnish compound of "rapa" (meaning "mud" or "sand", while rapautua means "to erode") and "kivi" (meaning "rock"), [ 1 ] because the different heat expansion coefficients of the ...
Quartz is a defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale . It is a common constituent of schist , gneiss , quartzite and other metamorphic rocks . [ 22 ]
Monzogranite – Biotite granite rocks that are considered to be the final fractionation product of magma – A silica-undersaturated granite with <5% normative quartz; Monzonite – Igneous intrusive rock with low quartz and equal plagioclase and alkali feldspar – a plutonic rock with <5% normative quartz
"Imperial Porphyry" from the Red Sea Mountains of Egypt A waterworn cobble of porphyry Rhyolite porphyry from Colorado; scale bar in lower left is 1 cm (0.39 in). Porphyry (/ ˈ p ɔːr f ə r i / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass.
A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental crust. [1] These rocks are primarily composed ofquartz, plagioclase, and alkali feldspar. [2]