ORIGIN OF THE IRON ORES. 
81 
Analyses of gas content of chalcedony associated with ore, of andesite, of volcanic 
emanations, and of the average of Jive crystalline rocks. 
A. 
B. 
C. 
D. 
H 2 S 
0.00 
13.93 
11.26 
.00 
4.00 
64.40 
6.44 
0.12 
13.93 
18.18 
.00 
3.63 
58.71 
5.43 
C0 2 
0.22 
34. 104 
CO 
2 
21.11 
.07 
56.70 
21.90 
8.422 
CH 4 
3.224 
H 2 
52. 134 
N 2 
2.072 
100.03 
.82 
100.00 
.82 
100.00 
99.958 
4.5 
A. Specimen 46613. Chalcedony in ore. From Crystal claim, Iron Mountain, Iron County, Utah. 
Analysis by Rollin T. Chamberlin. 0° C. and 760 mm. pressure. 
B. Specimen 46612. Andesite from Granite Mountain, Iron County, Utah. Analysis by Rollin T. 
Chamberlin. Same conditions. 
C. Gaseous emanations from Santorin. Analysis by Fouque. (Santorin et ses eruptions, p. 225.) 
When studied spectroscopically these gases were found to have traces of chlorine, soda, and copper. 
D. Average of five crystalline rocks. Analysis by Tilden. (Chem. News, November 9, 1897.) Stand- 
ard conditions. 
The gases in the chalcedony associated with the ore are roughly 
similar in their proportions to those of igneous rocks and volcanic 
conditions and differ generally in their proportions from the gases of 
the atmosphere. The gas analyses therefore furnish corroborative 
evidence of the introduction of the chalcedony directly from the late 
lavas. 
That iron was introduced into the underlying rocks by the hot lava 
solutions is shown by its intimate relations with the chalcedony in 
the jaspery phases at observed contacts of the lava and by its occur- 
rence in crystalline masses with chalcedony, partly or wholly filling 
cavities in the ore. The lava masses themselves are locally rich in 
iron. In the Antelope Springs area samples of the lavas (not veins) 
run as high as 6.5 per cent metallic iron. A few veins of magnetite 
and hematite are found in the lavas, which may have come from late 
lava solutions or from meteoric waters acting subsequently. The 
microscope discloses reaction rims about the biotite (as in the andes- 
ite, p. 48) formed during and following the flow of the lavas. The 
segregation of iron salts in the magma is further demonstrated by 
schlieren in the groundmass of the lavas, some of them light colored 
and some of them darker colored owing to a higher content of iron, 
and still further by the occasional segregation of magnetite or siderite 
about amygdaloidal cavities, both as fillings and as segregations in 
the adjacent groundmass. It is easy to conceive that iron salts got 
into the aqueous solutions which were in the lava at this stage of the 
cooling. 
The introduction of calcite, quartz, siderite, limonite, galena, 
barite, and copper carbonates from the lavas is well shown at Chloride 
Canyon, where immediately below the contact these minerals appear 
in veins or disseminated through the rock. Chlorite is not found 
28463— Bull. 338—08 6 
