Model of an Arizona Gold Mine 3 



the bright, yellow, glittering pyrite or iron pyrite 

 composed of iron and sulphur and the similar but 

 deeper yellow chalcopyrite, composed of iron, copper 

 and sulphur. 



The gold in this part of the mine is thinly dissem- 

 inated in invisible form through the sulphides. The 

 quantity of gold is very small. On the average, two 

 ounces of gold will be scattered through a ton of the 

 sulphides. Any substance of ordinary value so thinly 

 distributed would be worthless, as the expense of 

 blasting and raising the ore would much exceed what 

 it could be sold for. The value of gold is so great, 

 however, that even the small quantity in a ton of 

 sulphides is worth forty dollars, a value that well 

 repays working. 



THE GANGUE is the barren quartz which en- 

 closes the ore. In practice the terms ore and gangue 

 are somewhat loosely used. Thus one may describe 

 this material as sulphide ore in quartz gangue and 

 another may describe it as a quartz and sulphide ore. 

 Also the sulphide mineral with such quartz as is 

 extracted with it in the ordinary process of mining is 

 commonly referred to as the ore and only that quartz 

 which is extracted separately or is free from the sul- 

 phides is called the gangue. The gold is not equally 

 distributed through the sulphides. In some places the 

 sulphide will contain much more than the average 

 quantity of gold and in other places it will carry little 

 and in some places none. The sulphides without value 

 are not spoken of as gangue. They are called poor or 

 barren ore. In the upper levels, where the sulphides 

 are absent, the ore is that part of the quartz which 

 contains free gold, while the valueless portions of the 

 quartz form the gangue. 



One of the objects of a good miner is to extract 

 as much of the good ore as possible and at the same 



[3] 



