Geochemical and mineralogical study of bed load sediments will help to understand the weathering process, the intensity of weathering and the denudation in various environmental conditions, origin, mode of occurrence, biological and physic-chemical processes, mobilization and transport of various elements. River draining a single lithology helps to study above parameter of the catchment area. So here GumaniriverdrainingRajmahal basalt was selected as there is no report or literature available from this catchment to understand the weathering process in its water shade. The mineral compositions of the river bed load sediments from different locations shows quartz, calcic plagioclase, clinoenstatite clay minerals such as gibbsite, kaolinite, illite, goethite and clay micas, are dominating mineral phases. Clay mineral percentage is higher in the upper reaches compare to thelower reach of the river. Clay mineral gibbsite and kaoline indicate the removal of silica is higher in the upper reach and shows kaolintization, lateritization and upto some degree of Bauxitization process is active in the upper reach. CIA value, A-CN-K, A-CNK-FM ternary diagram indicate the intensity of weathering is moderate to high at different location. The index of lateritization shows clear indication of kaolintization?lateritization?Bauxitization process.