100 
INDEX. 
F. Page. 
Faulting, age of 68-69 
causes of 20 
character of 19-21 
occurrence of 7, 19, 21, 22-23, 43, 86 
Faults, plat showing 19 
Ferrous chloride, introduction and precipi- 
tation of 8, 77 
Fissures, character of 19-20 
depth of 86-87 
development of 9, 76, 86-87 
iron ore in 7 
views of 71,74 
occurrence of 19 
See also Andesite, fissures in. 
G. 
Gangue, character of 7, 70 
Gases, occurrence of, in rocks 80-81 
Geography, outline of 14-15 
Geologic column, figure showing 17 
See also Stratigraphy. 
Geologic history 7-9, 21, 85-86 
Geology, outline of 16-21 
Gilbert, G. K., on faulting 20 
on laccoliths T 47, 88 
Girty, G. H., fossils determined by 63 
Goldthwait, J. W.. and Huntington, E., on 
Iron Springs district 13, 
20-21, 23,62-63 
Gossan, inference from 94 
Granite Mountain, description of 16 
iron-ore deposits on, map of Pocket. 
location of 16 
section near 38 
Great Western claim, fissure vein on, plate 
showing 68 
fissure vein on, section of, figure show- 
ing 68 
map of Pocket. 
II. 
Harder, E. C, work of 12, 93 
Harmony Mountains, description of 14 
Hematite, occurrence of 7, 70, 90 
Henry Mountains, laccoliths of 47, 88 
Homestake limestone, age of 61-65 
analyses of 26-27 
character of 16, 25 
composition of, plates showing 28, 30 
contact phases of 27-34 
dip of 16, 37 
distribution of 24 
fossils of 37, 63 
fusion of 8, 78-79 
consequences of 8 
metamorphism of 8, 16, 25-37, 79, 84-86 
plates showing 26, 30, 48, 50 
mineralization of 27 
occurrence of 24 
sandy phase of 36-37 
specific gravity of , 34 
structural relations of 37 
thickness of 37 
Page. 
Hornblende-andesite breccia and agglom- 
erate, description of 53 
Hot springs, deposition by 43 
Howell, G. G., on Iron Springs district 12 
Huntington, E., and Goldthwait, J. W., on 
Iron Springs district 13, 
20,21,23,62-63 
I. 
Igneous rocks, correlation of 65 
occurrence and description of 46-61 
relations of ore deposits and 93-95 
See also Laccoliths. 
Iron, form of, in intrusions 8 
production of 11 
Iron City, iron development at 73 
Iron Mountain, description of 16 
iron ores on, maps of Pocket. 
location of 16 
mining claims on, map of . . 66 
Iron Mountain laccolith, section of, figure 
showing 69 
shrinkage of 20, 71, 86 
Iron ores, alteration of 75-78, 80-81 
analyses of 71, 73, 92 
character of 7, 9, 70-73 
comparison of, with Bull Valley ores .. 90-92 
with Lake Superior and Alabama 
ores 73, 95-96 
with miscellaneous ores 92-96 
composition of , plates showing. 28, 30, 48, 50, 72 
concentration of 75-82 
deposition of 9-78 
deposits of, maps of Pocket. 
depth of 7,66 
description of 66-74 
development of 73-74 
distribution of 66 
elevation of 66 
exploitation of 11 
exploration for 86-89 
extent of 7, 9-73 
investigation of 11-13 
occurrence of, modes of 7, 11 
origin of 75, 89 
See also Solutions, ore-bearing, 
relation of, to laccoliths. . 8, 75-79, 82, 84-85, 88 
to lavas 9,80-82,84-85 
to weathering 82-85 
sections of, figures showing 68, 69 
structural relations of 66-70 
tenor of 7, 71-72 
topography of 66 
types of 7, 67-70 
Iron-ore veins, plot of 19 
view of 74 
Iron Springs area, mining claims in, map 
showing 66 
Iron Springs district, geologic map and sec- 
tions of Pocket. 
investigations in 11-13 
location of 14 
map showing 15 
map of Pocket. 
Iron Springs Valley, view of 16 
