It is a group of metamorphic minerals - sillimanite, kyanite and andalusite. It may also contain sillimanite and graphite. These rock formations contain rich deposits of valuable minerals like coal, limestone, uranium and sillimanite. These include minerals such as coal, limestone, sillimanite, Kaolin and granite among others. These minerals include cordierite, muscovite, garnet, and sillimanite. The mineral sillimanite was named after Silliman in 1850. Other possible minerals formed at dehydration melting conditions include sapphirine, spinel, sillimanite, and osumilite. It occurs associated with staurolite, andalusite, sillimanite, talc, hornblende, gedrite, mullite and corundum. Andalusite is trimorphic with kyanite and sillimanite, being the lower pressure mid temperature polymorph. Granular sillimanite is available in beach sands of South India. Both the fibrous and traditional forms of sillimanite are common in metamorphosed sedimentary rocks. In 2004, India produced 14,500 tonnes of sillimanite and 6200 tonnes of kyanite. The metamorphic grades of aureoles are andalusite hornfels, sillimanite hornfels, pyroxene hornfels. Andalusite, kyanite, and sillimanite are naturally occurring aluminosilicate minerals that have the composition AlSiO. At higher temperatures and pressures, andalusite may convert to sillimanite.