Tonopah bonanza. [volume] (Butler City [i.e. Butler], Nev.) 1901-1909, 1904-07-23
MONTEzUMA DISTRICT.
Geology of the District that Pro.
duced High Grade Ores.

- 1RAh . GobiiE uI blNiC
n the Silver Peak region, in Esmer-
aida county, Nevada, published in
Bulletin No. 225 issued by the U. S,
Geological Survey, he might well
have included the old Montezama
mining district, which is interesting
as lying at the surface contact OF the
ancient limestones of Silver Peak
with the late rhyolites Of the Goldfeld
region.
The old camp Of Montezuma is sit
uated about fifteen miles e~ast-south-
east by the road from Silver Peak;
while Goldfeld is exactly six miles
due east. 1t is also about nine miles
southeast Of the Paymaster mine.
and twenty miles south Of the mines
on Lone Mountain referred to by Mr..
Spur.
The basal rocks of the district are
blue coralline limestones, either Cam
brian or Silurian, overlaid by a con
siderable thickness of continuous thin
beds of quartzite. The shales crop
chiefly in the higher c%entral portions
of the range, at attitudes varying
from 1000 to $500 feet above sea
evel, and are themselves capped on
the east by rhyolitic tufas, the peaks
of which rise to a height of from 8, 1000
to $500 feet with gentle slopes. The
rhyolite outbreak appears to have
followed a general north and south
line Of assuring, as the limestones
again outcrop 10 the valleys to the
ca st, being there capped by rocks
apparently andesitic.
About halfway between Montezuma
and Goldfield, a strong north and
south faults cuts off the sedimentary
rocks, those to the eastward being
very largely volcanic tufts, capped
by nearly horizontal beds of quartz
porphyry, having a nearly homogen-
eous paste, with smoky quartz crys-
tails. Where the road crosses the
fault, the rocks on the eastern side
are much broken, those in the imme-
date line of movement having been
extensively sillcifed, sheeted verti.
cally, and stained a brilliant red,
almost the color of minimum. Beyond
this fault to the eastward the road
follows the bed of a narrow, shallow
gulch, the north wall of which shows
thin beds of hinty ivory-white quartz,
breaking with a conchoidal fracture,
with a gentle dip to the east; these
are evidently the remains OF an ex.
tensive flow from hot springs. Thin
flakes of this white flint, as well as
of obsidian, are scattered all over
the district, along the trails used by
the Indians, in their annual visits to
collect pine-nuts, especially in shale
areas, where the shales have crum-
bled and made a soil of sufficient depth
to support a fair growth OF pinon and
juniper.
While no thermal springs are TO-
day in existence, the entire rhyolite
outcrop shows abundant remains OF
former activity. Much of the tufa
has assumed a pisolitic structure,
and large masses consist almost en-
tirely of little hollow spheres oil
chalcedony, the central core having
been removed after their formation.
either wholly or in part. Near the
actual line of contact with the shales,
bosses of the latter stand above the
surface, made up Of shale breccia,
cemented together and full of irreg-
uiar cavities; and a study of the vein
phenomena shows everywhere strong
hydro-thermal activity, with a ten
dency to dolomitization OF the lime
stones on important fracture lines.
There are a few outcrops of rocks
Of the basaltic series, which appear
in the shale area, but their relation
ship has not been worked out. None
were observed in the rhyolite or lime
stone exposures, SO theyare probably
older than the former. The coloring
of the rocks is characterize tic, the
limestones are blush gray, not yell
lowish brown as at Silver Peak; the
nr.aaniah oliun- h.nmn. al H.