74 



NATURE 



[March i8, 1920 



Relatively few properties are worked solely or 

 even mainly for silver, and only a small propor- 

 tion of the world's supply has of late years been 

 derived from them. It is therefore essentially a 

 by-product. The more important economic metals 

 with which it is most commonly associated are 

 g-old, copper, lead, and zinc. These five metals 

 tend to be gregarious, and many deposits contain 

 all of them. It is also found with tin, as in 

 Bolivia, and with nickel and cobalt, as in Ontario, 

 but such cases are uncommon. Although in dif- 

 ferent regions or in different parts of the same 

 region the above five metals are found in a great 

 variety of combinations, certain of these are par- 

 ticularly common. Thus gold and silver almost 

 invariably occur together either with or without 

 base metals. Again, lead and zinc nearly always 

 accompany each other, and ores carrying these 

 two metals, notably those in which lead pre- 

 dominates, are often richly argentiferous, the lead 

 and silver forming an especially characteristic 

 association. Copper in like manner is usually 

 accompanied by small quantities of gold or of 

 both gold and silver. The presence or absence 

 of base njetals in silver-yielding ores is of par- 

 ticular importance, since it determines the exist- 

 ing diversity in their metallurgical treatment and 

 occasions their classification into two groups, 

 known respectively as " milling ores " and " smelt- 

 ing ores," the former signifying those in which 

 the values are entirely or mainly in precious metal. 

 From the figures quoted in the report, it appears 

 that, broadly speaking, about two-thirds of the 

 world's supply of silver in 191 2 was obtained 

 from base metal, and one-third from precious 

 metal, ores. Further, only one-fifth was obtained 

 from mines worked exclusively for silver, while 

 four-fifths was derived as a by-product from mines 

 which were worked primarily for one or more of 

 the metals — gold, copper, lead, and zinc — and 

 would not have been in operation if their silver 

 had been the only metal present. Formerly, the 

 precious metal ores were the more important 

 source of supply, but in the last few decades more 

 and more of the metal has been won from base 

 metal ores. It will be seen, therefore, that the 

 authors, in endeavouring to estimate the future 

 production of silver, have been forced to take into 

 consideration the mining and metallurgy of four 

 other important metals as well. 



It is stated in the report that in 191 2 the New 

 World — i.e. the American Continent — furnished 

 82*5 per cent., and the Old World only 17-5 per 

 cent., of the mine production of silver. The output 

 in the British Empire was 21-7 per cent. Mexico 

 led with 32 o per cent., followed closely by the 

 United States with 283 per cent. Towards the 

 production of refined silver the New World con- 

 tributed 730 per cent., and the Old World 

 27-0 per cent., the contribution of the British 

 Empire being 18-2 per cent. The interesting fact 

 emerges that the United States of America refined 

 just about one-half the world's silver (496 per 

 cent.), whereas Mexico refined only 142 per cent. 

 NO. 2629, VOL. 105] 



More than half the Mexican mine production was 

 refined in the U.S.A., and very nearly the same 

 proportion of the Canadian output. It will be 

 seen, therefore, that the position now held by the 

 U.S.A., as the chief source of supplies of refined 

 silver, is one of considerable importance. The 

 same is true to an even greater extent for the 

 metals copper and zinc. 



The authors' view of the future is that if 

 normal industrial conditions are restored in 

 regions of curtailed production, a silver output at 

 least as great as any yet attained may reasonably 

 be anticipated. If, however, conditions affecting 

 industry in general, and mining and metallurgical 

 industries in particular, do not become favourable 

 in these regions, a long period must elapse before 

 the world's output can return to the previous 

 high-water level, and a still longer one before 

 the advance beyond that level interrupted since 

 1912 can be resumed. So long as the political 

 'conditions remain unsettled in Mexico, supplies 

 from that country will continue to be small. This 

 is particularly serious, because of the large dimen- 

 sions of the normal Mexican output. 



With the demand for silver more urgent than 

 any previously experienced, the restoring of the 

 mines and mills of Mexico to unhampered pro- 

 duction has become a matter of pressing inter- 

 national importance. It must be borne in mind, 

 however, that any extension in the mining of 

 precious metal ores will take time, and that the 

 mining of base metal ores is for the moment below- 

 normal, and will continue so as long as the surplus 

 supplies of copper, lead, and zinc produced during 

 the war remain unabsorbed. Silver production 

 will probably, therefore, remain for a time at a 

 low level. When, however, increased precious 

 metal mining reaches the production stage, and 

 the temporary check to base metal mining has 

 been removed, the authors anticipate a steady 

 increase in the output of the metal. 



It is well to remember that, although silver has 

 long occupied an important position as "second 

 string" among metals suitable for currency, there 

 are important industrial demands for it for other 

 purposes. It is only necessary to mention two 

 of these. First, in addition to the mechanical 

 properties which make it valuable as a currency 

 metal, there are others which have long been 

 known and utilised in the silversmith's art. 

 Standard silver lends itself readily to rolling, 

 stamping, spinning, and mechanical operations 

 employed in the manipulation of the metal in the 

 arts, and upon them important industries giving 

 employment to many workers are based. 

 Secondly, the well-known sensitiveness of silver 

 salts to light, made use of in photography, is 

 being increasingly utilised in the "moving 

 picture " industry, which in recent years has 

 absorbed a considerable proportion of the total 

 output of the metal. Both these industries are 

 formidable competitors for silver produced to-day, 

 and they will have to be reckoned with by future 

 Chancellors of the Exchequer. 



