GOLD MINING IN COLOEADO. 555 



method of occurrence of the gold, and the nature of the minerals with which 

 it is associated, as compared with the gold-bearing quartz of California, may 

 require slower crushing, especially where amalgamation in the battery is re- 

 lied upon for so large a portion of the product. Nevertheless, lighter stamps, 

 shorter drop, and increased speed are coming more into favor, and experience 

 will doubtless show in time what improvement is possible in this direction.^ 

 It may also be a question, not yet satisfactorily settled, whether or not there 

 would be greater economy in increasing the duty of the stamps and providing 

 better or more extended facilities for amalgamation outside of the battery, as 

 is the practice in some of the principal mining districts of California. 



Costs of Crushing. — Concerning the costs of stamping, the available 

 amount of statistical information is very meagre, because of the very little 

 attention that is generally devoted, in this region, to the classification of such 

 accounts. Many of the mills are placed at the mine, operated by the same 

 power and sharing with the mine the costs of fuel consumed; the ore, in 

 such cases, being delivered from the mouth of the shaft directly to the 

 stamps, without any exact record being kept of the quantity stamped. It is 

 generally estimated that ore can be treated for $20 per cord in steam mills, 

 while the average price, for custom work, is from $30 to $35 per cord. 

 Milling accounts, available to the writer, show that, in the mills to which 

 they refer, the actual costs were somewhat more than $20 per cord. Thus, 

 in the mill of the Ophir Company, working on the Burroughs lode, the mill- 

 ing costs, for several months of 1868, varied from $2 85 per ton to $4 62 per 

 ton, the average, for over 1,300 tons, being $3 69 per ton. This, allowing 

 seven tons and a half per cord, would make $27 67. In the mill of the Sen- 

 senderfer mine, during the month of August, the costs of milling 30 cords of 

 ore were stated by Mr. George T. Clark, the manager, at $700, equal to 



^ Li this connection the following comparative experience, related to the writer by 

 the superintendent of the Black Hawk mine, is interesting. The Black Hawk mill has 

 heavy stamps, running 15 drops per minute. The Eagle mill, near by, has lighter 

 stamps, running 30 drops per minute. Some time ago both mills were working on the 

 same ore, the loads being hauled alternately to either mill. The Eagle, with 20 stamps, 

 crushed nearly 15 cords of rock, while the Black Hawk, with the same number, only 

 crushed a little over 7 ; while the Eagle obtained nearly an ounce more bullion to the 

 cord of ore than the Black Hawk did. 



