Sillimanite!

SILLIMANITE

it is also called as Bucholzite . is ia an alumino-silicate mineral with chemical formula Al2SiO2. it is named after American Achemist Brjamin silliman (1779-1864). it is one of the three alumino-silicate : polymorphhs, kyanite & andalusite. 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 this section or even naked eye. both the fibrous & traditional forms of silicate are common in metamorphosed sedimentary rocks . it is an index mineral indicating a high degree of metamorphtism. sillimanite has been found in brandywine springs, new castle country, delaware, usa. it is also known as rock creek shear zone with the piedmont physiographic provience.

CHARACTERISTIC FEATURES :
CRYSTALLOGRAPHIC = orthorhombic
COLOURS = white, brown, green
LUSTRE = silky if in fibrous form, else vitreous
HARDNESS = 7.5
REFRACTIVE INDEX = 1.641-1.648
CLEAVAGE = 1
PLEOCHROSIM = colourless to pale brown to yellow
TYPE LOCALITY = wtava, susica, czech republic