Most of the rock is K-feldspar and quartz, and the dark crystals are a type of amphibole that is most common in felsic rocks. Felsic is an igneous rock term (it comes from combing parts of the words feldspar and silica) describing rocks forme from magma high in feldspars, silica and lighter colored materials. This broad grouping on the basis of mineralogy related to silica content is used in many modern classification schemes. Igneous rock - Igneous rock - Mineralogical components: The major mineralogical components of igneous rocks can be divided into two groups: felsic (from feldspar and silica) and mafic (from magnesium and ferrous iron). PLAY. This prevalence is the reason why felsic minerals melt at lower temperatures than mafic ones. Most granites are light gray to pink in color, but gray and dark red granites are common, too. Mafic rocks are darker in color than felsic rocks. The most general classification is based on the relative abundance in a rock of felsic (feldspar and silica-quartz) minerals vs mafic( magnesium and ferrum or iron) minerals. Which are definitions of “mafic” and “felsic”? Granite This medium-grained rock is a plutonic rock. Minerals. At the Earth's surface, those covalent bonds are much more stable and minerals like quartz tend to be much more resistant to weathering than olivine or pyroxene. a. Mafic is a magma/rock that is rich in feldspar and silica (quartz), whereas felsic refers to that which is rich in Fe and Mg. felsic. Mafic and Felsic, some igneous basics. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. ... quartz. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. Felsic minerals are usually light in color and have specific gravities less than 3. Mafic obsidians are scarce, but they have the same appearance. Quartz: Quartz is a common mineral in many metamorphic and felsic igneous rocks that, like plagioclase, also has a non-metallic luster and hardness greater than glass. Phaneritic ,Glassy 2. The most common felsic rock is granite , which represents the purified end product of the earth's internal differentiation process. Many parallel mafic and felsic bands are present in this area. Felsic rocks are mostly feldspar (especially K-feldspar), at least 10% quartz, and less than 15% mafic minerals (biotite, hornblende). Common felsic minerals include quartz, muscovite, hornblende, orthoclase, and the sodium rich plagioclase feldspars. Felsic <15% dark minerals: Very light in color, a bunch of quartz, potassium feldspar, very few dark minerals found. mafic minerals. Magma that has undergone a high degree of MAGMATIC DIFFERENTIATION has a composition consisting of FELSIC MINERALS (low temperature igneous minerals, such as quarts, K-spar, Na-spar, and mica. This one from Oahu is clearly not the most classic version of porphyry because it is mafic, it is extrusive, and the phenocrysts are mafic. Felsic – 1202 – 1472 degrees Fahrenheit . Felsic magmas are much more viscous than the intermediate magmas. Unlike plagioclase, however, quartz does not exhibit cleavage, which easily distinguishes it from feldspar minerals. In geology felsic refers to igneous rocks that are relatively rich in elements that form feldspar and quartz. Granite: Coarse-Grained Felsic Rock. plagioclase feldspar. Common felsic minerals include quartz, muscovite mica, and the orthoclase feldspars . There is little or no quartz. pyroxene, olivine, amphibole, and … Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica. The mafic magma crystallized as a fine-grained mafic tonalite containing more than 30 volume percent biotite, and locally, the felsic magma crystallized as coarse-grained felsic tonalite in small, agmatitic patches and veins in the mafic tonalite. The felsic minerals include quartz, tridymite, cristobalite, feldspars (plagioclase and alkali feldspar), feldspathoids (nepheline and leucite), muscovite, and corundum. calcite: hardness = 3 (not very hard), 3 cleavages not 90°, fizzes in dilute HCl. Compilations of many rock analyses show that rhyolite and granite are felsic, with an average silica content of about 72 percent; syenite, diorite, and monzonite are intermediate, with an average silica content of 59 percent; gabbro and basalt are mafic, with an average silica content of 48 percent; and peridotite is felsic. What is the difference between felsic and mafic rocks? quartz: hardness = 7 (hard), conchoidal fracture. Felsic igneous rocks are light in … FELSIC ROCKS. Felsic igneous rocks are light-colored, so a felsic obsidian seems a paradox. It is often assumed that phenocrysts that form the porphyritic texture must be felsic (feldspars (preferably alkali feldspars) or quartz). felsic minerals (quartz, K feldspar, etc) are light colored while - felsic minerals have the lowest melting points (600 to 750 °C) There is little or no quartz. Additionally, felsic magmas may have very high gas contents. The flattening of the fragments in the mafic bands suggests that this exposure is in the hinge of a fold. Quartz has a relatively low melting temperature, so magma with a higher silica content can form at much cooler temperatures relative to magma that contains denser elements such as iron or magnesium. You can't apply the term felsic to it. Felsic igneous rocks are silica rich and contain abundant potassium feldspar and quartz. Mafic magma progressively crystallizes and evolves while minimizing thermal and rheological differences. feldspars: hardness = 6 (hard), 2 cleavages at 90°. Mafic or hybrid magmas inject into felsic magma at low volume fraction (0.65) of crystals. potassium feldspar (k-spar): perthite (wavy lines) Composition Most Common Minerals Rock Name; felsic: glass (may contain a few minerals typical of felsic rocks) pumice: mafic: glass (may contain a few mineral typical of mafic rocks) There is more … West of the lake, a large outcrop was investigated (Figure 4.17); it is a fine-grained, massive, featureless white felsic rock with 1-mm clear-quartz eyes. mafic minerals. 1. Mafic rocks are abundant in the Earth's crust beneath the oceans. Gabbro is a mafic intrusive coarse-grained rock with allotriomorphic texture. Felsic 3. a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Felsic rocks Rocks composed mostly of biotite, muscovite, sodium-rich plagioclase feldspars, potassium feldspars, and quartz make up the felsic family of igneous rocks. Felsic rocks are mostly feldspar (especially K-feldspar), at least 10% quartz, and less than 15% mafic minerals (biotite, hornblende). Intermediate: 15-40% dark minerals: In between dark and light in color. All granites contain quartz and K-feldspar. Posted on August 31, 2014 by triplejunction. The term “felsic” refers to the high content of quartz laden feldspar minerals in the lava. Mafic lava creates basalt while felsic lava produces andesitic and rhyolite rocks. Felsic rocks are commonly oversaturated and contain free quartz (SiO2), intermediate rocks contain little or no quartz or feldspathoids (undersaturated minerals), and mafic rocks may contain abundant feldspathoids. Felsic definition, (of rocks) consisting chiefly of feldspars, feldspathoids, quartz, and other light-colored minerals. Which type of igneous rock would contain the most silica? If the K-feldspar is white, the granites are light gray; if the feldspar is pink or red, the granite is pink or red. 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