biotite
biotite An important rock-forming silicate mineral; a member of the mica group K2(Mg,Fe)6[Si3AlO10]2(OH,F)4, in which the Mg/Fe ratio is less than 2:1; biotite forms a series with phlogopite (of similar composition, but with Mg/Fe greater than 2:1) and may have Fe3+, Ti4+, and Al3+ also present in the formula; sp. gr. 2.7–3.3; hardness 2–3; monoclinic; black, dark brown, or greenish-black; vitreous to sub-metallic lustre; crystals tabular and pseudo-hexagonal, with lamellar aggregates and flakes; cleavage perfect basal mica; occurs in granites, syenites, and diorites, in schists and gneisses, in contact metamorphic rocks, and often in sedimentary rocks.
More From encyclopedia.com
Hornfels , Hornfels is a fine-textured metamorphic rock formed by contact metamorphism . Contact metamorphism occurs when a mass of hot magma intrudes into pree… wolframite , wolframite Ore mineral for tungsten, with the formula (Fe,Mn)WO4; sp. gr. 7.0–7.5; hardness 5.0–5.5; monoclinic; grey-black to brownish-black; browni… Igneous Rocks , Igneous rocks are formed by the cooling and hardening of molten magma. The word igneous comes from the Latin word igneus, meaning fire, and there are… Iron Ores , Rocks
Rocks are composed of minerals, which are natural inorganic (nonliving) substances with specific chemical compositions and structures. A rock m… Rock , rock1 / räk/ • n. 1. the solid mineral material forming part of the surface of the earth and other similar planets, exposed on the surface or underly… Country Rock , Country rock
The term country rock refers to a body of rock that receives or hosts an intrusion of a viscous geologic material. Intrusions into count…
About this article
biotite
All Sources -
You Might Also Like
NEARBY TERMS
biotite