Firstly, the visual method. The category of building materials can be determined in accordance with the size of fractions, as well as the presence of all kinds of impurities. For verification, you can use a small sieve, the cells of which have a different size — from 0.1 to 0.5 millimeters. You need to sift a small amount of sand. This will establish the category and type of material. If there are large particles of clay in the sieve, then this is a sign that you got the cheapest sand.