Clay deposits become one of the natural mineral sources used abundantly as cost-effective raw materials for various industrial productions in recent years that use depend mainly on their quantification done by rational analysis. The rational analysis is a reliable and optimization method for the quantitative determination of all mineralogical components and structural formulae of the clay minerals that furnishes all their properties. However, no work reports the aspect of the quantitative analysis of the clay minerals deposited in Nepal. Considering the facts, the present work targeted to carry out the rational analysis of a bulk (BC), fine (FC), and HCl-activated Thimi white clay (FCHCl) sample specimens to explore its potential uses in all industrial sectors, based on their chemical and mineralogical analysis data. Vermiculite, K-mica minerals with feldspars and quartz as assessors confirmed qualitatively in the Thimi white clay sample specimens, and their quantification of all the mineralogical components and their ionic structural formulae successfully estimated at present. The quantitative amounts of the iron-bearing vermiculite and K-mica minerals are increased with decreases of the quartz and Na-mica in the fine clay particles compared to the bulk clay sample. Acid-activated fine clay particles would apply as a suitable raw material for the quality production of white-wares on an industrial scale.