Sillimanite: Biotite gneiss (Mesozoic and Paleozoic)

Sillimanite

Sillimanite also called Bucholzite is an alumino-silicate mineral with the chemical formula Al₂SiO₅. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Sillimanite is named after the American chemist Benjamin Silliman (1779-1864). Benjamin Silliman ( 8 August 1779 &ndash 24 November 1864) was an American Chemist, one of the first American professors Year 1779 ( MDCCLXXIX) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Common Year 1864 ( MDCCCLXIV) was a Leap year starting on Friday (link will display the full calendar of the Gregorian Calendar (or a Leap year

Occurrence

Sillimanite is one of three alumino-silicate polymorphs, the other two being andalusite and kyanite. Polymorphism in Materials science is the ability of a solid material to exist in more than one form or Crystal structure Andalusite is an Aluminium nesosilicate Mineral with the chemical formula Al2SiO5 Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich A common variety of sillimanite is known as fibrolite, so named because the mineral appears like a bunch of fibres twisted together when viewed under thin section or even by the naked eye. Both the fibrous and traditional forms of sillimanite are common in metamorphosed sedimentary rocks. Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) It is an index mineral indicating a high degree of metamorphism. An index mineral is used in geology to determine the degree of Metamorphism a rock has experienced

Sillimanite has been found in Brandywine Springs, New Castle County, Delaware, USA. Delaware ( is a state located on the Atlantic Coast in the Mid-Atlantic region of the United States. By suggestion of the members of the Delaware Mineralogical Society, it was named by the State Legislature in 1977 as the Official Mineral of Delaware. It is also known from the Rock Creek Shear Zone within the Piedmont physiographic province of the District of Columbia, USA. Sillimanite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism.

Details

See also

• Andalusite
• Kyanite
• List of minerals
• List of minerals named after people

External links

• WebMineral entry