Coal deposits in Mexico were firstly recognized back in 1850, the main coal deposits in Mexico are located north of the Coahuila State. Coal samples from coal mines of Sabinas Basin were collected and analyzed for chemical composition, separation characteristic and calorific value (CV). The analytical data indicate that the coals usually have low or high ash content (Ash), 17 – 50 wt %, depending on the sample source. Comparison of the calorific value with both ahs content and fixed carbon, indicate that these two parameters are directly connected together: the higher the calorific value of coal, the lower the ash content and high fixed carbon content. Rejection of the ash using sink-flotation technique and their ratio whit the calorific value (CV/Ash) was evaluated in this study. Also, the ratio of Calorific value to fixed carbon (FC) was analyzed. Washability analyses for selected coal sample (+1 ½”, -1 ½” + ½”, -½” +¼“, - ¼“ + 1/16”, -1/16” +#100, size group) using heavy organic liquids with a density from 1.3 to 1.6 gr/cm3, were carried out. Calorific value-ash (%)-Fixed Carbon relationship was presented. The results indicate that the ratio CV/Ash vs. specific gravity has an exponential behavior, whereas the value of the ratio CV/FC was found to be 117.3.