20 Colorado Gold Mines. [T -:*.'.: = rv. 



The gold caught on the plates is, under the most favour- 

 able circumstances, only 40 per cent of the assay value of 

 the ore. The quantity of silver saved is inconsiderable. 

 The gold from the blankets, and that in the buddle concen- 

 trate, does not amount to more than 5 per cent more ; so 

 that, when treating even the most tractable of these sul- 

 phurets, battery amalgamation and tailing concentration do 

 not secure more than 45 per cent of the gold, and therefore 

 involve the loss of 55 per cent of the gold, and of all the 

 silver, copper, and lead. As alread}? stated, it is the second 

 class ore, or that from which has been separated by hand 

 the solid sulphurets, and from which has been thrown away 

 stuff too poor for treatment, that is milled. 



The benefit of tailing concentration is so insignificant 

 from the simple fact that it is so carelessly and rapidly con- 

 ducted, that only the very largest and heaviest particles can 

 sr::le in the voluminous and swift stream of water used. 

 Most of the tailings carry more than 1 oz. of gold to the 

 ton, about 2 per cent of copper, and 15 per cent of iron 

 7 ::es and blende galena. The concentrate will consist of 

 almost pure iron pyrites very little — if any — more copper 

 than the crude tailings contained, and seldom as much as 

 2 ozs. of gold. Mr. Baker gives the average contents in 

 gold of 45 samples of tailings, from assaj s made by reliable 

 assayers, Messrs. Schulz and Burlingame, at 27*86 dols. per 

 ton, — the highest assay being 50*40 dols., the lowest 2*21 

 dols. : 38 samples of dressed tailings contained on an 

 :age, according to the same authorities, 42*90 dols. The 

 heavy iron py : it E 5 is increased four to five times by the concen- 

 tration as effected now ; the lighter copper pyrites, carrying 

 the gold, is washed away into the stream. The first act of 

 reform should doubtless be — dress the tailings from the 

 present mills on the same system that slimes are dressed 

 the world over. 



In Gilpin County there are scattered over the hill-sides, 

 at the mines, or in the river valleys, where water runs, but 

 where — through perverse mismanagement — steam is never- 

 theless often employed as the motive power, about 70 mills, 

 with 1300 stamps. Of these many have been idle ever since 

 they were built, and at the best of times not more than half 

 the number of stamps have beeu in operation. At the pre- 

 sent moment, owing to the special but evanescent causes of 

 depression already explained, there are not 30a stamps 

 running. But in 1868-9, wnen Gilpin County produced 

 :_ 17,900 dols. in gold, and in 1869-70, 1,378,100 dols. in 

 gold, the average number of stamps running throughout the 



