The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.
They are usually light in color and have specific gravities less than 3. The most common felsic rock is granite, but others include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. In terms of chemistry, felsic rocks are on the other side of the rock spectrum from the mafic rocks.
In modern usage, the term acid rock, although sometimes used as a synonym, refers to a high-silica-content (greater than 63% SiO2 by weight) volcanic rock, such as rhyolite. The term was used more broadly in older geologic literature. It is considered archaic now, as the terms "acidic" and "basic rock" were based on an incorrect idea, dating from the 19th century, that silicic acid was the chief form of silicon occurring in rocks.
The term "felsic" combines the words "feldspar" and "silica". The similarity of the term felsic to the German words Fels, meaning "rock", and felsig, meaning "rocky", is purely accidental, as feldspar is a borrowing from German Feldspat, which derives from German Feld, meaning "field".
Read more about Felsic: Classification of Felsic Rocks
Other articles related to "felsic":
... rock dominated settings with abundant felsic rocks and less than 10% mafic material ... settings are often shale-rich siliciclastic-felsic or bimodal siliciclastic ...
... Mineralogic contents - felsic versus mafic felsic rock, highest content of silicon, with predominance of quartz, alkali feldspar and/or feldspathoids the felsic minerals these rocks (e.g ... mafic rock, lesser content of silicon relative to felsic rocks, with predominance of mafic minerals pyroxenes, olivines and calcic plagioclase these rocks (example, basalt, gabbro) are usually dark coloured, and ... both to their composition and mode of occurrence Composition Mode of occurrence Felsic Intermediate Mafic Ultramafic Intrusive Granite Diorite Gabbro Peridotite ...
... In order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals namely quartz, orthoclase and plagioclase ... Rocks with greater than 90% felsic minerals can also be called leucocratic, meaning 'light-coloured' ... In some cases, felsic volcanic rocks may contain phenocrysts of mafic minerals, usually hornblende, pyroxene or a feldspar mineral, and may need to be named after their ...
... Felsic (or silicic) lavas such as rhyolite and dacite typically form lava spines, lava domes or "coulees" (which are thick, short lavas) and are associated with pyroclastic (fragmental) deposits ... Felsic magmas can erupt at temperatures as low as 650 to 750 °C ...
... These felsic protocontinents (cratons) probably formed at hot spots from a variety of sources mafic magma melting more felsic rocks, partial melting ... subordinate ultramafic, volcanic rocks, and mostly younger subaerial and submarine felsic volcanic rocks and sediments were oppressed into complex synforms between rising young domiform ... uncommonly thick volcanic accumulations from which voluminous partial-melt, low-density felsic rocks could be generated ...