Knowra Biotite Biotite Biotite is a dark mica-group sheet silicate rich in potassium, iron, and magnesium. It commonly occurs in igneous and metamorphic rocks and splits into thin, flexible sheets.
Mica : Mica is a group of sheet silicate minerals that cleave into thin, flexible sheets. Biotite is the dark, iron- and magnesium-rich member of this mineral group.
Crystal structure : Crystal structure is the ordered, repeating arrangement of atoms or ions in a solid. Biotite’s crystal structure organizes its tetrahedral and octahedral sheets into layers.
Petrography : Petrography is the description and classification of rocks, especially through microscopic examination. Biotite’s color, cleavage, and optical properties help identify minerals in thin sections.
Muscovite : Muscovite is a light-colored potassium mica rich in aluminum and poor in iron and magnesium. Its pale color and chemistry contrast with biotite’s dark, iron- and magnesium-rich composition.
Phyllosilicate : A phyllosilicate is a silicate mineral built from sheets of linked tetrahedra. Biotite’s defining structure is the stacked-sheet architecture of phyllosilicates.
Isomorphous substitution : Isomorphous substitution occurs when ions of similar size replace one another in a crystal structure. Substitutions among iron, magnesium, aluminum, and other ions create biotite’s compositional range.
Igneous rock : Igneous rock forms when molten rock cools and solidifies. Biotite occurs in many granites and other intermediate to felsic igneous rocks.
Phlogopite : Phlogopite is a magnesium-rich mica with little iron, commonly found in magnesium-rich rocks. It is a lighter, more magnesium-dominant mica in the same broader mineral family.
Silicate mineral : A silicate mineral contains silicon–oxygen units as a principal part of its structure. Biotite belongs to the largest and most diverse mineral class.
Ferromagnesian mineral : A ferromagnesian mineral contains substantial iron and magnesium in its composition. These elements give biotite its dark color and distinguish it from light-colored micas.
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