SECONDARY ENRICHMENT OF SILVER ORES 3 
the solubility, and still others have assumed the agency of carbon- 
ate waters. At greater depths, the precipitation has been thought 
to be due to the action of hydrogen sulphide or of other sulphides, 
to the reduction of sulphate solutions by organic matter, or to other 
causes. The work described in this paper was undertaken to test 
some of the hypotheses mentioned and to discover if possible in 
the laboratory the actual extent and speed of the reactions that 
were found to take place. While much remains to be done, the 
results herein presented are such as to indicate with some degree of 
certainty the probable reactions which take place in the solution 
of silver ores by meteoric waters, and, to a less extent, those which 
occur in their precipitation. 
DEFINITION OF TERMS 
The terms “primary” and “‘secondary”’ have not always been 
employed with precise meaning and their use is likely to be attended 
with some confusion. Wherever introduced into this paper, they 
are used in a genetic sense. Unless otherwise indicated, the term 
“primary” implies the agency of hot ascending waters; ‘‘secondary,”’ 
that of cold meteoric waters. It is commonly recognized that 
some silver ores have been deposited by the agency of cold sulphate 
solutions in rocks devoid of sulphides.t Such deposits might be 
termed primary, but in their chemical aspects they are secondary, 
since they differ from those which ordinarily would be termed 
secondary only in the distance the silver solutions have been carried 
and in that they have been deposited outside of some zone of 
primary minerals. As regards their origin through the solution of 
some truly primary silver mineral, their method of transportation 
in solution, and the methods of their precipitation, they do not 
differ from ores precipitated in a silver lode after having been trans- 
ported a short distance. 
SCOPE OF THE DISCUSSION 
A study of the literature of silver deposits brings out the fact 
that all of the silver minerals except the chloride may have either 
a primary or a secondary origin. These minerals include, in addi 
tW.H. Emmons, ‘‘The Cashin Mine, Montrose Co., Colo.,’’ U.S.G.S. Bull. 285 
(1905), 125. 
