Felsic
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In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium and iron.
A felsic volcanic lithic fragment, as seen in a petrographic microscope. Scale box is in millimeters.
Close-up of granite from Yosemite National Park.
A specimen of rhyolite.
Volcanic rock
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Volcanic rocks are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic ro
Ignimbrite, a volcanic rock deposited by pyroclastic flows
Photomicrograph of a volcanic lithic fragment (sand grain); upper picture is plane-polarized light, bottom picture is cross-polarized light, scale box at left-center is 0.25 millimeter.
An aphanitic volcanic sand grain, with fine-grained groundmass, as seen under a petrographic microscope
Vesicular olivine basalt from La Palma (green phenocrysts are olivine).