sillimanite (fibrolite) A nesosilicate and one of an important group of three mineral polymorphs with the same composition Al2SiO5, the other two being andalusite and kyanite; sp. gr. 3.23; hardness 6.5–7.5; orthorhombic; occurs as elongate prismatic crystals with a diamond-shaped cross-section or as fibrous and felted masses; colourless; occurs under conditions of high-grade metamorphism either in the innermost zones of thermal aureoles (see CONTACT AUREOLE) or in high-grade regional metamorphic rocks (see REGIONAL METAMORPHISM) formed under high temperatures and pressures. It is named after the American mineralogist B. Silliman.
More From encyclopedia.com
Metamorphism , Metamorphism is the process by which the structure and mineral content of rocks transform in response to changes in temperature , pressure , fluid co… Schist , Schist Schist is a metamorphic rock consisting of mineral grains that are more or less aligned in layers. Because of this structure, schist tends to… Migmatite , Migmatite A migmatite, or "mixed rock" in Greek, is a banded, heterogenous rock composed of intermingled metamorphic and igneous components. Veins, c… Wollastonite , enstatite (En) An important orthorhombic pyroxene (orthopyroxene, or opx) Mg2Si2O6 and end-member of an isomorphous series, the other end-member bein… Shock Metamorphism , Except for certain laboratory experiments and outdoor detonations of high explosives (including nuclear weapons), evidence of shock metamorphic condi… 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…
About this article
Updated About encyclopedia.com content Print Article
You Might Also Like