Clay minerals are the most important industrial minerals whose application is dependent on its structure and chemical composition. Mineralogical, chemical compositions, phase constitutions, and microstructural morphology of certain clay minerals from three different deposits in south western Nigeria were investigated using state-of-the-art equipment. These were done with the intention of determining the appropriate application for the clay minerals. It was observed that the major phases in the clay samples from the three different deposits are kaolinite, microcline, muscovite/illite, plagioclase/albite and quartz. These phases were observed in varied percentages. It was concluded that sample A (Ifon clay) which contains very low kaolinite (5.63%); could not use for making high temperature caliber refractories. But due to its high content of feldspar, it could be processed for the production of feldspar for glass and iron making industries. Sample B is considered to be appropriate for the production the refractory composite due to its most appropriate content of both kaolinite (23.74% kaolinite) and feldspars (26.12% microcline and 11.28% plagioclase/albite) which is necessary for producing mullite fibers in ceramic matrix at a temperature of around 1400^oC. Sample C (Iseyin clay), which contains very low feldspars (3.00% microcline and 3.08% plagioclase/albite) and high content of kaolinite was considered suitable for further processing for making high temperature caliber refractories.