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Rhyolite (/ ˈraɪ.əlaɪt / RY-ə-lyte) [1][2][3][4] is the most silica -rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase.
This is called a silica tetrahedron. In a magma that is low in silicon, these silica tetrahedra are isolated, but as the silicon content increases, silica tetrahedra begin to partially polymerize, forming chains, sheets, and clumps of silica tetrahedra linked by bridging oxygen ions. These greatly increase the viscosity of the magma. [47]
Pumice is composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock.It is commonly [4] but not exclusively of silicic or felsic to intermediate in composition (e.g., rhyolitic, dacitic, andesite, pantellerite, phonolite, trachyte), but basaltic and other compositions are known.
The term "Strombolian" has been used indiscriminately to describe a wide variety of volcanic eruptions, varying from small volcanic blasts to large eruptive columns. In reality, true Strombolian eruptions are characterized by short-lived and explosive eruptions of lavas with intermediate viscosity, often ejected high into the air. Columns can ...
Igneous differentiation. In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is ...
Colloidal silica is used as a fining agent for wine, beer, and juice, with the E number reference E551. [22] In cosmetics, silica is useful for its light-diffusing properties [42] and natural absorbency. [43] Diatomaceous earth, a mined product, has been used in food and cosmetics for
Diorite. Diorite (/ ˈdaɪ.əraɪt / DY-ə-ryte) [1][2] is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is intermediate in composition between low-silica (mafic) gabbro and high-silica (felsic) granite.
Dacite (/ ˈdeɪsaɪt /) is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz.