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Template: Igneous rocks. ... Download QR code; Print/export ... Category:Igneous rocks This page was last edited on 22 May 2023, at ...
Trachyte – Extrusive igneous rock – A silica-undersaturated volcanic rock; essentially a feldspathoid-bearing rhyolite; Troctolite – Igneous rock – A plutonic ultramafic rock containing olivine, pyroxene and plagioclase; Trondhjemite – Light-colored intrusive igneous rock – A form of tonalite where plagioclase-group feldspar is ...
Grain size in igneous rocks results from cooling time so porphyritic rocks are created when the magma has two distinct phases of cooling. [18] Igneous rocks are classified on the basis of texture and composition. Texture refers to the size, shape, and arrangement of the mineral grains or crystals of which the rock is composed. [citation needed]
Mineralogical composition of igneous rocks with decreasing silica (SiO 2) content. The rock names for volcanic/extrusive and plutonic/intrusive rocks are written above. Notice that this is a rough way to determine a rock name: the exact difference between the given igneous rocks does not only depend on silica content. Date: March 2009: Source ...
Color index, as a geological term, is a measure of the ratio between generally dark mafic minerals and generally light felsic minerals in an igneous rock. [1] [2] The color index of an igneous rock is the volume percentage of mafic minerals in the rock, excluding minerals generally regarded as "colorless" such as apatite, muscovite, primary ...
Phaneritic (phaner = visible) textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye.
Igneous rocks include rocks that have solidified from a melt either below the surface of a planet or natural satellite as intrusives or on the surface as extrusives or volcanic eruptions. The main article for this category is Igneous rock .
English: Graph of mineral content, by percentage, of various igneous rocks.The dotted line on the figure represents one such value, where roughly 2% quartz, 6% alkali feldspar, 54% plagioclase feldspar, 2% pyroxene, 21% amphibole, and 15% mica suggests a rock of intermediate composition, either andesite or diorite (depending on crystal size and other factors).