GOLD MINING m COLORADO. 



561 



small, in fact, but is left out of the account altogether hy the banker who pur- 

 chases the bullion. 



Date. 



No. tons of ore. 



Assay value in coin per ton. 



a 

 



s .s 



==■ 8 



Percentage of 

 total value 

 obtained. 



Percentage of 

 gold value 

 obtained. 



Gold. 



Silver. 



Total. 



1869. 



September ■ 



Week ending October 16 . 

 Week ending October 23 . 

 Week ending October 30 . 

 October 9 to January i, 1870 



Four lots amount- 

 ing to 316 tons. 



87 

 60 J^ 



77 

 0850 



$23 35 



20 04 



24 80 



22 73 

 2583 

 20 67 



23 77 



25 13 



I3 36 



1 56 



15 08 



15 47 

 3 90 



2 86 

 2 99 

 I 94 



$26 71 

 21 60 

 39 88 

 38 20 

 29 73 

 23 53 



26 75 



27 07 



§10 00 

 12 00 



6 50 



9 85 

 12 32 



7 72 

 9 00 



10 50 



37-0 

 55-0 

 i6-3 

 26.0 

 41.4 

 32.8 

 33.6 

 39-0 



42.8 

 60.0 

 27.0 

 43.0 

 47.0 

 37.0 

 38.0 

 41.0 



a Includes the three lots foregoing. 



From this it appears that the proportion of gold obtained varies from 

 27 to 60 per cent, of the quantity originally contained in the ore, leaving 

 from 40 to 73 per cent, remaining in the tailings. This is, of course, based 

 on the assumption that the original assays of the ore fairly represent its true 

 value. This may or not be the case, as the difficulty of obtaining fair average 

 samples of such ore has been already pointed out, and the apparent vv^ant of 

 uniformity in the results of working the several lots of orcj quoted in the 

 table, is itself one indication of this difficulty ; but making all due allowance 

 for this, the general result of the experiments may be regarded as an approx- 

 imation to a truthful expression of the relation existing between the value and 

 the yield of the ore in tbe case referred to. It would, however, be unfair to 

 accept this result as the expression of that relation in the case of all the ores 

 in the district, inasmuch as this experiment is based on the working of ore 

 from only one mine in a single mill ; and, further, the average yield of the 

 ore in question is 25 per cent, less than that already shown to be the average 

 yield of milling ores throughout this region. 



As a check upon the original assay of the ore the manager of the same 

 mine has recently caused some assays to be made of the taihngs, or residue of 

 the ore after it has been milled. The following are the results of two dif- 

 ferent lots : 

 71 



