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For instance, biotite occurs in the lava of Mount Vesuvius and in the Monzoni intrusive complex of the western Dolomites. Biotite in granite tends to be poorer in magnesium than the biotite found in its volcanic equivalent, rhyolite. Biotite is an essential phenocryst in some varieties of lamprophyre.
Biotite is a rock-forming mineral found in a wide range of crystalline igneous rocks such as granite, diorite, gabbro, peridotite, and pegmatite. It also forms under metamorphic conditions when argillaceous rocks are exposed to heat and pressure to form schist and gneiss.
Sep 2, 2023 · 1. Igneous Rocks: Biotite commonly forms in igneous rocks, particularly in the following settings: Granite: Biotite can be a significant component of granite, where it crystallizes from the cooling magma. The presence of biotite in granite contributes to its characteristic dark color.
Aug 26, 2023 · Biotite: Biotite is another dark-colored mineral that is sometimes found in granite, accounting for up to 5% of the rock’s composition. It is a type of mica that gives granite a dark, almost black color.
Biotite is a common rock-forming mineral, and is especially noted in metamorphic rock s such as schist and gneiss. It is also found in igneous rock such as granite s and rhyolites. Biotite is also the primary mica in rare earth pegmatite s. Rock Type. Igneous, Metamorphic.
Jan 4, 2024 · Biotite Granite. Biotite granite is rich in biotite mica, which gives it a dark color, often in shades of brown or black.
Biotite and muscovite are the two most common mica minerals that often occur together in Al-rich igneous rock. Peraluminous two-mica granitoid. A fragment from an erratic on Alnö Island, Sweden.
Jan 16, 2020 · It is found in the lava from Mount Vesuvius, the Monzoni intrusive complex of the Dolomites, and in granite, pegmatite, and schist. Biotite is so common that it's considered a rock-forming mineral. If you pick up a rock and see glittery flashes, there's a good chance the sparkles come from biotite.
In plain light, biotite in a granite appears a slightly drab brown. Radiation damage from zircon can leave pleochroic spots that fade to extinction at a different rate that the surrounding, undamaged material.
Biotite granite Rocky Face Quarry Prospect, Hiddenite, Alexander County, North Carolina, USA
