262 ARTHUR LAKES 



red Jura-Trias beds of sandstone are often stained with copper, 

 but rarely yield copper in workable quantities. In Butte, 

 Montana, from which many millions of pounds of copper 

 have been extracted, the ore comes from a small granitic 

 area, a mile wide, by two miles long on the western slope of 

 the Rockies. The distribution of the ore is irregular, exten- 

 sive bodies being found on breaking through an apparently 

 well defined wall. There is often no defined Ime between vein 

 and country rock. The ore occurs in chutes extending for 

 several hundred feet along the strike before pinching out. The 

 depth of these chutes is often greater than their length. The 

 veins may be from a few inches to 100 feet in thickness of 

 ore, 5 feet to 6 feet being the average. 



The outcrop of the vein appears as a brownish iron stain- 

 ed quartz passing down with depth into red and yellow 

 oxides carrying gold and silver. These decomposed ores 

 extend down towards water level 40 to 300 feet, and then 

 begins the rich zone of secondary copper ores. The copper 

 minerals of this zone pass through all the gradations from 

 pure rich copper glance to copper pyrites and iron pyrites; 

 bornite, or purple copper, appears as a conspicuous element. 



These secondary ores diminish in value with depth and 

 again this diminution lessens with greater depth; the ore 

 is said to average 6 per cent copper and five ounces silver to 

 the ton of 2,000 pounds. The Butte mines, however, make 

 more profit from their 6 per cent ore than formerly from ore 

 double that richness, owing to improvements in treating ore. 

 At a depth of 1,300 feet there is no sign of waning. 



The earliest knowledge of copper in the southwest was 

 from Mexicans who, in the latter part of the last centur}^, dis- 

 covered the Santa Rita mines in New Mexico, near the present 

 town of Silver City. The Mexicans called these mines Crea- 

 dera del Cobre, the place where copper was created, the native 

 metal cropping out on the ground. Masses a ton in weight 

 were extracted and shipped to the City of Mexico to be coined 

 into copper money. In 1838 the Apaches drove out the 

 miners, and not until 1873 were the mines resumed under 

 American management. In 1865 Colonel Carleton's Califor- 

 nia volunteers pursuing Indians discovered Copper mountain, 



