Arizona republican., 1901-08-02
DRESSING AND CONCENTRATION
A. W. Warwick Writes of Scientific
 Ore Treatment.

A. w. Warwick, an English capital isi interested in mining in western Ari- zona and southern California, writes this article on ore dressing and conccn- tration for the Mining Reporter:
 In the previous article some figures were given to show the importance Of the subject and the growth of the sci ence. In this a;Licle the methods of sep aration will be briefly discussed. h classifying the various methods of sep aration We find that, practically speak, ing gil mineral properties are taken advantage of Specific gravity, hard ness. chemical properties. magnetic qualities are the chief characteristics which play part. Chief of these, Of course, is the variation in specific grav- ity. and up to quite recently this was the only property taken advantage of. Broadly speaking, machines that sep arated minerals according to the diff ference in specific gravities have reach ed the highest possible perfection. h. Ventors are, therefore, T1yirg more and more attention to other mineral proper ties In order to make separations in those cases where the machines refer red to do imperfect W Ork. As examples of this reference may be made to the separation Of spathic iron ore and zinc blende of tin ore and wolfram. In the case of spathic iron and zinc blende we may consider the specific gravities as practically identical. To be commer- II tod and to do this the magnetic qualities of the iron ores are taken advantage Of. After slight calcinltion spathic iron ore becomes intensely magnetic, but the bende is unaffected, thus the iron is readily removed and leaves the zinc ore behind in a high state of purity. In the case of tin ore and wolfram the spe Cfic gravities are equal, and in this case the mixed ore is CalCiUed with sulphatc of soda, which combines with the wolf ram to form tungstSte of soda, but does not affect the tin orc. Tungstate of soda being soluble In water the sep aration is readily secured by that agen- Cy, leaving the pure tin ore behind. Many similar mixtures of ore are known which would be Of great value if only some method of treatment could be devised, and no doubt many of thes@ problems will be solved by taking ad- vantage of other mineral characteristics than difference of specific gravity.
 No reference has been made to the part played by the purely physical Charac.eristics of minerals. such as col or, luster, crys alline forms, etc. These D bnWnN-ot. nf hla in,Inrst anCe, as will be shown hereafter, es- pecially in the operation of hand sort ing. However, it not only in making separations by hand that such proper ties are useful, but also in allowing the ore dresser and conCentrGtor to make rapid dei erminations of the quality of his work. In many mills 1t is unneces- sary to check the work by assays, eX- cept for selling the products or in giv- ing accurate figures on the value of the ore sent to the mill and the value of the tailings leaving the mill. The men op- erating the mill can tell b. purely phy- sical products their machines are mak. ing whether good work is being done or not. and thus correct, if necessary, the adjustments of the machinery. This is rendered possible by the physical properties of the minerals color, luster and texture.
 Whatever may be lhe method of sep aration p is essential to crush the mix ed minerals fine enough so as 10 break loose the minerals each from the other. rms operation, besides being the first. is by far the most important. since if it is improperly performed TO separating machine that may be used. however ef- hcient, will make good savings or sep aiations. If choice were given be- tween tWo systems, one with imperfect crushing arrangements and perfect sep alators, another with a perfect crush Ing plant and separators not as cffi- cient as in the first case then the sec ond arrangement would he the writer's cholce. The crushing problem is made more difficult by the fact that with few exceptions, the valuable mineral is gen eraily soft and in encased in a hard matriX; for example. galena in quartz. In such case sufficient force has to be applied to the ore in order to crush tho harder mineral. and in so doing thc more fragile mineral is frequently broken to a fine slime, rendering it's saving very difficult.