COMPARISON OF IRON SPRINGS ORES WITH OTHER ORES. 93 
purpose simply to emphasize the widespread distribution of deposits 
of these types and to cite some of the descriptions. 
From the fact that the ores of these districts have certain essential 
features in common, it does not necessarily follow that the origin of 
the ores has been the same for all. Certainly there has not been 
enough detailed work on the ores of many of the localities named 
to warrant final conclusions as to their origin. Nevertheless, the 
similarities in these deposits are such as to suggest similarity of origin 
as a guiding hypothesis for study, and such results as have been 
obtained to the present time tend strongly to support this hypothesis 
rather than to break it down. 
Several deposits which have been examined personally by the 
writers or associates are unhesitatingly assigned an origin similar to 
that here presented for the Iron Springs district of Utah. These 
include the Taylor Peak and White Pine ores of Colorado, studied by 
Van Hise and Leith and mapped in detail by Harder and Ward ; the 
Cebolla district of Colorado, examined by Van Hise and Leith; the 
Bull Valley district of Utah, examined by Leith and Harder; and 
certain of the deposits in northeastern Washington, Texada and Van- 
couver islands, the Kamloops district, British Columbia, and San 
Bernardino County, California, examined in reconnaissance by 
Leith. All of these ores, in hand specimen and slide, show intimate 
association with anhydrous silicates and have structural relations to 
wall rock essentially similar to those of the Iron Springs district, 
though differing from these in structural and lithologic details. 
Among the men who have given particular attention to the eco- 
nomic geology of the west emphasis has been uniformly placed on 
the genetic association of ores and igneous rocks along contacts, but 
there has been lack of agreement as to the real significance of the 
association — as to whether the igneous rocks have contributed both 
solutions and ores, or only hot water which has leached the ores 
from the adjacent rocks, or only heat which has enabled meteoric 
waters to leach ores from the adjacent rocks and redeposit them; 
whether the solutions have been liquid or gaseous; what their direc- 
tion of movement has been, etc. In recent years there has been a 
rapidly growing tendency to emphasize the importance of liquid and 
gaseous solutions coming directly from the igneous rocks and bring- 
ing the ores with tkem. In discussions of genetic classifications of 
ores by Lindgren, a Weed, 6 Spurr, c and others, ore deposits developed 
along igneous contacts by "pneumatolytic after-action" find con- 
a Lindgren, Waldemar, The character and genesis of certain contact deposits: Trans. Am. Inst. Min. 
Eng., vol. 31, 1902, pp. 226-244. 
6 Weed, W. H., Ore deposits near igneous contacts: Trans. Am. Inst. Min. Eng., vol. 33, this. pp. 
715-746. 
c Spurr, J. E., A consideration of igneous rocks and their segregation or differentiation as related to 
the occurrence of ores: Trans. Am. Inst. Min. Eng., vol. 33, 1903, pp. 288-340. 
