Mineralogy and Petrology of the Krishna Godavari Basin on Shore Area, East Coast of India

Shales are defined as fine-grained terrigenous sediments and rocks that contain 50 % or more of terrigenous, and generally argillaceous, clastic components less than 0.062 mm in size. In the shales, clay-size components often dominate their rock properties, such as density, plasticity, parting, compatibility and swelling. Generally the size boundary between clay and silt is 4m, but most clay minerals are less than 2 m size siltstone, clay stone and mudstone are broadly called shales. XRD patterns of whole - rock of Raghavapuram shale/clay sample indicate the predominating presence of kaolinite and quartz, with minor chlorite, muscovite, and illite. Iron mineral peaks were not observed, indicating that no hematite / magnetite was incorporated in the clay minerals. Smectite and chlorite are present in trace amounts in some of the samples. Identification of secondary minerals was difficult, because their peaks overlapped by the greater peaks of the major minerals such as kaolinite and quartz. Semi-quantitative analyses, following to method modified after Schultz (1964), showed differences in bulk mineral compositions between the individual samples. Samples richer in kaolinite being poorer in quartz. Some of the samples contain only small amounts of feldspar.