Gravity  separation  of  natural resources  presents method of separation of useful minerals from  barren rock according to difference in their density. Gravity separation is the ancient method  of preparation  of natural resources  used before 2 thousand years before Christ, and during alluvial mining of  tin and gold at the South Ural and Altai in 14-16 centuries there were developed the gravity separation apparatuses , which were the prototypes of the modern equipment ( for instance K. Frolov gold washers). One of the first of scientific reasoning of gravitation separation was given by M.V. Lomonosov.

Gravity separation  obtained the widest distribution at the end of  19 and at the beginning of the 20-th century, when output of natural resources sharply increased. Gravity separation is actual even nowadays, which is connected with its principle advantages – cheapness and possibility of separation mineral particles of  different range of sizes ( from 0,1 up to 300 mm) by different methods. Gravity separation is carried out in water and air medium.  In water medium the separation is performed more precisely due to higher density of water. During gravity separation usually earth gravitational force is used is used which became a reason of naming this method of separation.
Simultaneously with  gravity force sometimes centrifugal and electromagnetic forces are used.

Theory of gravity separation is based on definition of relative  travel speeds of particles, differ with density and sizes, in medium of different density. For the first time the theory of gravity separation was developed by P. Rittinger ( 1867). Essential development the gravity separation  obtained in Papers of G. Ya. Doroshenko  (1876), S>G. Voyslav (1884), V.A. Guskov (1908), R.Richards (1908). T. Finkey (1940), and especially , P.V. Lyashchenko (1940). Firstly there were developed methods of definition of  falling velocity of single particles. Separation takes place at sufficiently high difference of speeds: the particles of higher density are located at the bottom, and particles of less density – in the upper part of layer. With such approach for separation particles on density it is necessary that particles should have relatively close sizes ( otherwise very large particle of low density will be falling with the same speed as small particle of higher density , therefore separation will not occur). However, in practice this principle was not observed , but the separation took place. The experts tried to eliminate discrepancy between theory and practice by introducing idea of the so called  constrained conditions of particles travel, in which they move in group. But in this case it is very difficult to take into account regularities of mutual friction and travel of particles. The experts also tried to consider the gravity separation process as separation of large particles in dense suspension of finer particles.

The modern theory of gravity separation was developed in 60-th by the Soviet scientists E.E. Rafaels-Lamark, N. N. Vinogradov, etc. The main attention is paid to analysis of stratification as mass statistic process and  to properties of suspensions being in statistically unsteady condition.

Varietie of gravity separation are jigging, preparation in heavy suspensions, concentration on tables and sluice boxes, preparation in hydraulic cyclones, chutes, etc.
 

Reference literature : P. V. Lyashchenko , Gravity methods of separation, 2-nd edition, M.-L.,