GENERAL CHARACTER OF THE ORE DEPOSITS. 
silver values. The ore deposits of these camps, if not demonstrably 
of contemporaneous origin, were formed by physically similar 
waters. The original sulphides include stephanite, iron pyrites, 
and chalcopyrite. Pyrargyrite, also noted, may be secondary. 
From the primary ores free gold, horn silver, malachite, azurite 
limonite, and hematite are derived. The relative abundance of 
silver sulphides or of pyrite determines whether the veins carry pre- 
dominant silver or gold values. In the same camp structurally 
similar veins may carry either gold or silver and in various parts of 
the same vein the proportion of the two metals differs greatly. A 
little calcite is associated with quartz in some veins, and at Silver- 
bow and Eden quartz bodies suggestive of the crystal form of cal- 
cite probably indicate its former presence. Irregular zones or areas 
surrounding these veins are either silicifled or kaolinized, the former 
process having been contemporaneous with ore deposition, the latter. 
In certain cases at least, subsequent to it. The contact with the vein 
quartz is in some cases transitional, in others sharp. In all the 
amps these zones of altered rock are much more extensive than the 
ore deposits, and ore deposition unaccompanied by either silicifica- 
tion or kaolinization has apparently not occurred. The silicifled 
rhyolite is white in color, flinty in texture, and without prominent 
phenocrysts, although careful inspection shows the presence of quartz 
phenocrysts, while weathered surfaces show feldspar casts. In 
some instances the slightly smoky quartz phenocrysts alone re- 
tain their identity. Some of the altered rhyolite is so dense that the 
Indians have used it in making arrowheads. During the deforma- 
tion of the rocks after siliciflcation the brittleness resulting from the 
(tensity of this conchoidally fracturing rock was an important factor 
n the production of numerous cracks which furnished channels to 
>«urfaee oxidizing waters. Cavities of solution and the interstices 
)f brecciated zones are lined with clear quartz crystals or filled with 
martz masses. The alteration has taken place along joints and 
faults and in bands between joints. The silicifled rhyolite, being 
Inch more resistant to weathering than the unaltered rock, stands 
p in rugged walls and knobs whose extent is coincident with that of 
he siliciflcation. The peculiar topography resulting is well seen in 
he domical hills three-fourths of a mile east of north of Silverbow. 
Iere there are rugged walls from 1 to 5 feet high, while cro^s walls 
how that siliciflcation has also occurred along minor fractures be- 
ween the main joints. 
•tinder the microscope the silicifled rhyolite shows a mosaic of 
uartz or chalcedony notably uneven in grain, while coarser mosaics 
r limonite-lined cavities represent the biotite and feldspar pheno- 
irysts, although in some specimens biotite is replaced by muscovite 
nd limonite. The silicifled rhyolite of the Cactus Range, south of the 
