SECONDARY ENRICHMENT OF SILVER ORES 54 
been made of the waters of gold and silver mines. For them the 
writer is indebted to Professor W. H. Emmons who has very kindly 
placed at his disposal the data which he is about to publish concern- 
‘ing secondary enrichment. The figures given are in parts per 
million. 
. Geyser silver mine, Custer Co., Colo., 500-foot level. 
. Same, 2,000-foot level. 
. Comstock lode, Savage mine, 600-foot level. 
. Comstock lode, G. and C. shaft, 2,250-foot level. 
. Comstock lode, Comstock mine, vadose water. 
. Comstock lode, Gould and Curry mine, 1,700-foot level. 
. Comstock lode, Hale and Norcross mine. 
. Comstock lode, Gould and Curry mine, 1,800-foot level. 
9. Nevada City, Cal., Federal Loan mine, 400-foot level. 
10, Nevada City, Cal., Black Prince mine, 400-foot level. 
11-14. Rothschonberger Stolln, Freiberg, Germany. 
15. Creede, Colo., Bachelor mine, 1,300-foot level. 
16. Creede, Colo., Solomon mine, 1,500-foot level. 
17. Idaho Springs, Colo., Stanley mine. 
18. Tonopah, Nev., Mizpah mine; water from a bore hole 2,316 feet deep. 
or AM BPW ND H 
A study of these data shows clearly that the salts most abundant 
in mine waters are the sulphates, and further, that there is usually 
present an excess of acid radicles over basic; i.e., the solutions are 
acid in most cases. The preceding analyses are all of waters taken 
at some depth, hence must be assumed to be much more nearly 
neutral than the waters near the surface, since the tendency of 
descending waters is to become less acid through reaction with 
minerals. At Creede, as will be noted, the waters at the 1,500- 
foot level have actually become alkaline through the solution of 
carbonate in excess. It is a significant fact that this level is below 
the zone of secondary enrichment.* 
The amount of ferric and ferrous salts present in the waters, 
as shown by the analyses, is surprisingly small. This is probably 
to be explained by the fact that iron salts are- very easily pre- 
cipitated by carbonates, which are here present in large amount. 
On the whole, the analyses tend to confirm the hypothesis that the 
active agents in the secondary processes are acid sulphate waters. 
They would also suggest that carbonate solutions may be a factor 
*W. H. Emmons, unpublished manuscript. 
