LiNDGHEN] COPPER DEPOSITS AT CLIETON, ARIZ. 139 
less extensive zone of chalcocite or copper glance, deposited by sec- 
ondary processes on the pyrite. 
The most important vein system is that which, under the general 
name of the Humboldt vein, extends from northeast to southwest 
through Copper Mountain at Morenci. The outcrops of this vein are 
practically barren, but at the depth of about 200 feet the deposit 
becomes productive and contains chalcocite associated with pyrite. 
There are usually one or more central seams of massive chalcocite, 
some of which are fairly persistent. These seams are ordinarily 
adjoined by decomposed porphyry, now chiefly consisting of sericite 
and quartz, together with pyrite and chalcocite. These extensive 
impregnations of the country rock are rarely confined by distinct 
walls, but gradually fade into the surrounding porphyry. That 
these deposits are genetically connected with fissure veins can, how- 
ever, not be doubted. In lower levels the ore is apt to change to 
pyrite and chalcopyrite. Both the Arizona Copper Company and the 
Detroit Copper Company are now working the low-grade bodies of 
chalcocite ore accompanying the veins. The reserves thus far opened 
assure a high production for many years to come. 
Parallel veins, somewhat narrower, but similar in character, are 
those opened by the Arizona Central mine, also at Morenci. These 
veins are partly in porphyry, partly in contact metamorphosed lime- 
stone. While malachite and azurite sometimes occur, they are by no 
means as prominent as in the limestone deposits, and frequently the 
leached surface zone is immediately adjoined by the chalcocite ore. 
The Coronado mine represents a different type of deposits. It is 
formed on a fault fissure between granite and quartzite, indicating a 
throw of at least 1,000 feet. The fissure is followed in places by 
a diabase dike, showing some effect of crushing and movement on 
the vein. The croppings contain copper carbonates and silicate, but 
these minerals change at slight depth to chalcocite, and still farther 
| down it is believed that the ore bodies consist chiefly of pyrite and 
chalcopyrite. 
Somewhat different again are the fissure veins on Markeen and 
Copper King mountains. The granite of this complex of hills is cut 
by a great number of porphyry dikes which generally have a north- 
easterly direction. Along many of these dikes movement and As- 
suring has taken place, and varying amounts of copper ores have 
been encountered. The veins contain comparatively little gangue, 
the copper minerals being chiefly distributed through the altered por- 
phyry or through the granite adjoining the dike. At the surface a 
small amount of carbonates may be found, but they change at slight 
depth, sometimes only a few feet from the surface, into an ore com- 
posed of chalcocite and pyrite, which still farther down appears to 
change into pyrite and chalcopyrite. The most prominent deposit on 
this system of veins is the Copper King mine, which is situated only 
