Occurrence of Andalusite in a Quartz Vein Near Mallegowdanahalli, Bangalore District, Mysore State

Andalusite occurs in a quartz "Vein intrusive into ultrabasic rocks altered to tremolite-actinolite schists, on a low mound about half a mile to the SE of Mallegowdanahalli, Doddaballapur Taluk, Bangalore District, Mysore State and about 35 miles to the NNW of Bangalore. Andalusite is formed along the margins of the quartz vein as a result of reaction between the quartz and alumina-rich magmatic vapours, following the intrusion of the quartz vein, in the presence of magnesia and lime available in the surrounding ultra basic schists. Corundum has formed in the final stages of the pneumatolytic activity and is deposited in the fracture planes of andalusite. Continued activity by potash-rich hydrothermal solutions at the closing phases of the magmatic processes has partly transformed the andalusite and corundum into dumortierite, muscovite and pyrophyllite.