108 ECONOMIC GEOLOGY 



fusion. All these minerals occur native and as alloys, principally 

 as scales or granules in the placer gravels, in the same location as 

 described under the caption of platinum. The geological horizon 

 is the same as given for platinum. 



LOSSES OF PRECIOUS METALS 



The losses of precious metals may be classed as follows: 

 (1) Hoarding. The quantity hoarded is indeterminable, and 

 the loss is largely retrievable. (2) The amount put out of circu- 

 lation as objects of art and ornamentation. (3) Wear and tear. 

 This represents an irretrievable loss. It occurs in the wear of the 

 coin whereby the medium of exchange to-day meeting the stand- 

 ard of weight, to-morrow becomes too light, as its edges and sides 

 have become smooth. The coin is not suitable as a medium of 

 exchange, and it goes back to the United States mint for recoin- 

 age. This loss also occurs in the gold leaf, silver leaf, wire, and in 

 the pure metals used extensively for plating. (4) Loss in the 

 useful metals, that is, ores containing too low a percentage of 

 gold, or silver, or both, to separate with a profit. A small per- 

 centage of these metals goes into the useful metals as copper and 

 iron, from which it is never removed. (5) The concentrates 

 from milling processes from which other metals are recovered 

 may carry so small a percentage of either gold or silver that 

 they are thrown directly into the waste, thereby losing, for 

 all commercial purposes, a certain quantity of silver and gold. 

 (6) In the extraction of the metals, as reducing the ore to a pulp 

 too rapidly, in crushing the ore too coarsely for amalgamation 

 to take place, and in the employment of cheap labor. (7) Loss 

 in tailings. In some plants estimation has been made that from 

 50 per cent, to 60 per cent, of the actual gold and silver present 

 in the ore is lost in the tailings from the mill. If the loss in 1 

 gal. of water is 0.018 cent, and if 576,000 gal. of water per day 

 represents the amount of waste, the actual loss for one year would 

 be represented by the following: 



576,000X0.018X360X2 = 174,649.60. 



(8) By crushing the ore too finely. This produces a flour gold 

 and silver, both of which are carried away on the surface of the 

 water. (9) By filling the holes in the stamps and pans with amal- 

 gam. (10) By cleaning the plates too quickly. (11) Byremov- 



