Currency of using the method of magnetic control of ferrous impurities for construction materials was noted. Especially it is important because of magnetic separators which are widely used for elimination of these impurities. There were shown the necessity of upgrading the present approach in order to realize the method of magnetic control. For example, it is necessary to take into account not only the rest of ferrous impurities (that is inevitable after limited numbers of operations) but also a factor of involving sand particles. The concrete proposal how to develop the existing system of magnetic control of ferrous impurities in construction materials subjected to magnetic separation, is stated. The experimental-calculation model for such control is also shown. The main parameters of such model were estimated on the example of quartz sand and feldspar. The errors of standard methods of magnetic control were revealed for the first time.