Mode of Occurrence and Distribution of Bauxite Deposits in Andhra Pradesh and Feasibility of Aluminum Industry

Abstract

Bauxite forms four groups of capping in high hills of the Eastern Ghats which are form SW to NE the Gurtedu group, Chintapalli group, Paderu group and Araku (or Anantagiri) group in a belt 130km long and 20km wide. It occurs both on Khondalite and charnockite. The capping on the khondalite are more in number than on the latter. The in situ formation of bauxite by alteration on khondalite is indicated by the relict foliation of khondalite in bauxite, parallel to the foliation of the underlying khondalite, the pseudomorophs of the bauxite mineral gibbsite after garnet, silliminate and feldspar and the boulders with core of fresh rock and cover of bauxite. Boehmite differs from diaspore in that it has a lower specific gravity and occurs in the form of minute crystals (rhombic or bladed) which can only be seen with a microscope. Both minerals, if separated from impurities are usually colourless. Gibbsite (or hydragillite) is the only alumuna mineral found in trihydrated bauxites both in the crystalline and non-crystalline forms. It is colourless like the monohydrated minerals but has a lower specific gravity (2.35).Aluminium manufacture consists of two phases, i.e., manufacture of alumina from bauxite (Al2O3) and the alumina is to be refined and fabricated. The location of the smelters is being controlled by the location of the ore deposits and the power sites. The ore moves to power if they are wide apart as this industry is very power intensive and the cost of transportation determine the exact site. From the alumina by electrolysis process aluminium is manufactured by the application of cryolite, India is being used to import entirely from S.W.Greenland. At present synthetic Cryolite is being used as a substitute which is prepared from fluorspar. Alumina is a light metal and can stand long haulage. Hence the source of power has become the most dominant factor for the location of aluminium plants which subsequently fabricate the aluminium.