By Chisom Ibemere
Staurolite is a silicate mineral which is produced by regional metamorphism in rocks such as mica schists, slates, and gneisse. It is associated with other minerals such as kyanite, garnet, and tourmaline. Staurolite is brittle and hard mineral with a dull lustre.
Staurolite has dark brown crystals which are often twinned in cruciform patterns that can be made into ornaments. The name “Staurolite is gotten from the Greek word stauros, which means cross and lithos for stone in reference to the common twinning.
Staurolite may occur in places like Canada; North Carolina, Virginia, and Georgia, U.S.; Brazil; Brittany, France; and Switzerland, especially along the Saint Gotthard Pass.
Staurolite may be dark brown, brownish-black, red-brown in colour with a sub vitreous and resinous Lustre. It has a mohs hardness of 7 – 7½, Specific Gravity of 3.74 – 3.83 and a Monoclinic crystal system. Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. Magnesium, zinc and manganese substitute in the iron site and trivalent iron can substitute for aluminium.
Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs with almandine garnet, micas, kyanite; as well as albite, biotite, and sillimanite in gneiss and schist of regional metamorphic rocks.
Staurolite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism. They are used as an abrasive mostly in sandblasting, and as foundry sand. They may also be used in cutting and etching monumental stone, as filler material in paint primers and as a source of alumina for cement production.
