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Sep 2, 2023 · Biotite is the most common mica mineral and also known as black mica, a silicate mineral in the common mica group. Approximate chemical formula K (Mg, Fe). It can be found in massive crystal layers weighing several hundred pounds.
Jan 16, 2020 · Key Takeaways. Biotite is a dark-colored mica. It is an aluminosilicate mineral that forms sheets or flakes. Although biotite is sometimes called black mica, it occurs in other colors, including brown, greenish-brown, yellow, and even white. Biotite occurs with other types of mica, even within a single rock.
Biotite, also known, as ‘black mica’ is a rock-forming femic phyllosilicate that occurs in several igneous and metamorphic rocks. The mineral was named in honor of the French scientist Jean-Baptiste Biot, who devoted his life to study the optical properties of the micas.
Biotite, a silicate mineral in the common mica group. It is abundant in metamorphic rocks (both regional and contact), in pegmatites, and also in granites and other intrusive igneous rocks. For chemical formula and detailed physical properties, see mica (table). Biotite is regarded as a mixture.
A common, widespread, rock-forming mineral, biotite is a significant mineral in granites, diorites, and igneous pegmatites. In pegmatites, biotite crystals can be very large. It also occurs in schists, gneisses, and hornfels that resulted from either regional or contact metamorphism.
Chemical Formula: K (Mg,Fe++)3 [AlSi3O10 (OH,F)2. Composition: Molecular Weight = 433.53 gm. Potassium 9.02 % K 10.86 % K 2 O. Magnesium 14.02 % Mg 23.24 % MgO. Aluminum 6.22 % Al 11.76 % Al 2 O 3. Iron 6.44 % Fe 8.29 % FeO. Silicon 19.44 % Si 41.58 % SiO 2. Hydrogen 0.41 % H 3.64 % H 2 O. Oxygen 43.36 % O. Fluorine 1.10 % F 1.10 % F.
Biotite is present in both silica under- and oversaturated rocks. Biotite, because it is the host of relatively uncommon chemical elements in a given magma, is a very common ingredient of pegmatites which crystallize from late-magmatic fluids. Large “books” are a common sight in pegmatitic rocks.
