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In contrast to generally observed non-acidic and less weathered Mollisols in temperate semi-arid and humid climate, acidic and fairly weathered Mollisols on Deccan basalt are observed in hills of central (Satpura Range, Madhya Pradesh) and Western India (Western Ghats, Maharashtra) under forest in the present tropical humid climatic conditions. The detailed morphological, chemical and mineralogical investigations of these Mollisols of central and western India indicates that due to the presence of zeolites in the Deccan basalt, the transformation of smectite to kaolinite was prevented and the retention of adequate amount of smectite and continuous supply of calcium ions from zeolites made the formation of Mollisols in forest even under tropical humid climate. The formation and the persistence of these Mollisols in association with acidic Alfisols under sparse forest in the basaltic landscape of millions of years in central and western India demonstrates the primary importance of the quality of parent material rich in expanding clay mineral and bases in their formation. This unique example thus expands the basic knowledge on the formation of Mollisols in the humid tropical part of the world. (c) 2006 Elsevier B.V. All rights reserved.