156 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
The original sulphide ores from which the oxidized ores have been 
derived consist of pyrite containing variable amounts of chalcopyrite. 
These pyritic ores are sometimes directly in contact with oxidized 
ores, but it is not uncommon to find masses of chalcocite between the 
two. Bornite has been reported from some of the ore bodies, but 
arsenical or antimonial compounds are absent, so far as known. 
Origin of the ores. — That the original ore deposition was genetically 
connected with the intrusion of the granite-porphyry is reasonably 
certain. The present incompleted investigation, however, has not yet 
established the details of this connection. As a whole, the ore bodies 
may be classed as typical replacement deposits in limestone. 
The ore bodies that have thus far proved workable have resulted 
from the operation of later processes of concentration acting upon the 
original pyritic ores. The occurrence of the chalcocite is closely 
related to the general progress of oxidation, and this mineral has 
plainly been formed by the action of descending solutions upon lean 
pyritic ores. It is probable that at least a .part of the chalcopyrite is 
ascribable to the operation of the same agency. There is an observed 
connection between good ore and permeability to downward-moving 
solutions. Such pyritic ore as proves profitable is soft and crumbling 
and usually shows upon close examination interstitial sooty material 
that is probably amorphous chalcocite. 
The lower limit of oxidation of the ores is very irregular, and is 
apparently uncontrolled by any constant groundwater level. In the 
Calumet and Arizona mine oxidized ore occurs at a depth of a thou- 
sand feet, while residual masses of sulphide ore occur in the adjoining 
Copper Queen mines within 150 feet of the surface. Masses of lean 
pyrite are sometimes inclosed in an envelope of high-grade chalcocite 
and oxidized ores. 
FUTURE OF THE DISTRICT. 
Although more or less mineralization occurs at many points in the 
Mule Mountains, there is little to indicate that any deposits of copper 
ore will ever be found to approach in importance those already known 
and awaiting discovery in the faulted limestone syncline about Sacra- 
mento Hill. For over twenty years the Copper Queen mine has pro- 
duced an average of more than 16,000,000 pounds of copper annually. 
Recentty the Calumet and Arizona Company has begun energetic 
operations in ground almost surrounded by the property of the Coppei 
Queen. Not onl}< is there sufficient known ore in these mines to keep 
them in operation for many years to come, but there is no evidence! 
that the bottom of the ore-bearing ground has been reached in any oi 
these extensive workings. Moreover, the statement maybe venturer 
that the specter of the "lower lime" has hitherto had an undue infiu 
ence in restricting prospecting to horizontal planes. There is cer 
tainly a reasonable hope of finding ore bodies in the Devonian anc 
