Tourmaline occurs as a minor but important mineral in the alteration zone of the Archean orogenic gold
deposit of Guddadarangavanahalli (G.R.Halli) in the Chitradurga greenstone belt of the western Dharwar
craton, southern India. It occurs in the distal alteration halo of the G.R.Halli gold deposit as (a) clusters of
very fine grained aggregates which form a minor constituent in the matrix of the altered metabasalt
(AMB tourmaline) and (b) in quartz-carbonate veins (vein tourmaline).