Classifiers are used for separating various sizes of solid particles using a liquid. The materials used here are slurries of fly-ash, gravel and cement which are coarse and fine particles of range between densities of sand (2024 kg/m3) and coal (946 kg/m3). These particles undergo certain unit operations like sieving, mixing, filtration and drying, before final stage. Focus is also on finding the efficiency of the cone classifier. Classifiers find applications in de-gritting operations of drilling mud and in de-sliming of minerals prior to floatation, separation of clay from barites in drilling mud, sizing of sand into fractions, removal of impurities and ungrounded particles from chalk, de-gritting of underground waters. They have largely replaced mechanical classifiers in closed-circuit grinding. This work is aimed for utilization by researchers, industrialists’ and traditional businesses. Apart from this it will be especially relevant and useful for the students of Metallurgy, Mining, Mechanical engineering and Chemical engineering for carrying out research in the area of classification of solid particles and also the design and usage of cone classifier.