MINERALS FROM THE CLIFTON-MORENCI DISTRICT, ARIZONA, 
By W. Lindgren and W. F. Hillebrand. 
In 1902 an examination was made of the Clifton-Morenci eoppel 
district in Arizona. Study of the collections proved the presence of 
several interesting minerals, a brief account of which is here given.* 
The copper deposits at Clifton and Morenci consist partly of irregular 
or tabular bodies of oxidized ores in Paleozoic limestones, partly of- 
chalcocite ores connected with fissure veins in a granite-porphyry o»i 
in the same limestones. 
CORONADITE. 
On the dump of a small shaft on the west end of the Coronado vein.i 
three-fourths of a mile west of Horseshoe shaft, fairly large amounts! 
of a dark metallic mineral were found intimately intergrown with 
quartz and decomposing into limonite. The vein at this end shows nc 
copper minerals, but is said to contain some gold, and its surface ore,' 
are reported to have been worked in an arrastre in the early days ol ; 
the camp. In color this mineral is black and its structure is delicately 
fibrous. The hardness is about 4 and the streak black with brow nisi 
tinge. 
A thin section proves it to be opaque, and in reflected light its fibrou; 
and homogeneous structure is well brought out. It cements angula J 
quartz grains and its secondary nature is clearly indicated. In gen 
eral aspect it is not unlike psilomelane. A preliminary examinatioi 
showed that it contained the oxides of lead and manganese. As it di< [ 
not seem to correspond to any known mineral species, an analysi 
was made, after a partial mechanical separation. The results were a 
follows: 
Long-continued efforts to procure pure material for analysis by th 
use of heavy solutions were not attended with success. The ultimat 
product of specific gravity, 5.246 at 22°, yielded on decomposition b" 
hydrochloric acid a residue of from 6 to 7 per cent, which consiste I 
mainly of silica, with a small amount of alumina, etc. Its presenc i 
would not have mattered much had it been quite indifferent to acid* , 
but its partial solubility, as shown by the varying amounts undissolve l| 
on different trials, and similar varying amounts of alumina and perliaj - ! 
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