GOLD MINING IN COLOEAUO. 



559 



mines or mills incur the expense of weighing anything but first-class ore; 

 the stamp rock is roughly measured as so many wagon loads, or car loads, 

 and the quantity expressed in wood-choppers' terms as so many '' cords." 

 The weight of a cord of ore is variable, depending on its character. A cord 

 of quartz, or poor vein-rock, unmixed with heavier minerals and broken in 

 fragments of the size suitable for stamps, when loosely packed in a wagon or 

 measuring box, would hardly weigh more than six tons and a half, or, if more 

 closely packed, seven tons. A cord of pure iron pyrites, broken and packed 

 in same manner, would weigh nearly twice as much. The weight of a cord 

 of ore, therefore, depends on the proportion of pyrites mixed with the rock 

 and the degree of fineness to which the stuff" is broken, or the amount of 

 space in the measuring box unoccupied by solid matter. According to these 

 conditions a cord may weigh seven, eight, or nine tons or more. The aver- 

 age of seven and one-half is probably not far from the truth. 



The difficulty of getting at the yield, precisely, is still further enhanced 

 by the fact that it is commonly stated in "ounces." This means ounces of 

 crude bullion, or retorted amalgam, which varies in value according to the 

 amount of silver, base metals, and other impurities contained in it, and, as 

 has been already shown, may be between $12 or $13 and $18 in coin. This 

 value, moreover, may be expressed by some mill-men in coin, by others in 

 currency, the relation of which to coin is also variable, so that to obtain 

 the desired information, with something like a satisfactory degree of pre- 

 cision, demands a persistent inquiry that sometimes appears to a busy mill- 

 manager to be an unwarrantable curiosity about other people's affairs. 



Considering the cord of ore equal to seven and one-half tons, and the 

 average yield of the cord six ounces of retorted amalgam, worth $16 50 per 

 ounce, the average yield of the ton of rock may be stated at $13 20 in coin. 

 This accords very closely with the average deduced from the statements of 

 many of the mill-men, which, as shown in the table of milling operations, 

 amounts to $13 30, coin, per ton. 



Estimating the average yield of the cord of ore at seven ounces and one- 

 half of amalgam, as some do, the yield per ton would be one ounce, or 

 $16 50 in coin. This, of course, refers to stamp-rock, leaving the first-class 

 ore out of the question. 



