The Weiser signal. [volume] (Weiser, Idaho) 1890-1904, 1902-02-27
EXAMINED MINES FOR DEWEY
uas Seen SO to 81 From One Pan of Dirt and
$4,000 Ore--Dewey Mill Averages $96.
CovELo, CAL. Sept. 25, 1901.

Dear Sir:-ln reply to your re-
ouest, | have in the accompanying
article connected all the information
7 have as yet been able to obtain
concerning the auriferous deposits of
Idaho county, State of Idaho, known
90 Thunder Mountain. These mines
are situated in a region composed
entirely Of volcanic rocks, whose
position approximates the horizontal,
and cover an area of several square
miles. The predomlnating rocks are
rhyolitc. The main body of rhyo-
lite is of great thickness and is over
laid with breccia whose fragmental
constituents are well rounded. The
rhyolite is interspersed with dykes
of phonolite, lying within the bed
ding planes of the strata.
The chief ore bearing vein of the
district traverses the s'Golden Reef
mine. 1t is here we'll exposed by
hydraulic workings. This claim was
laid out in an easterly direction and
westerly direction upon somewhat
obscure outcrop of q dyke of phon-.
olite, fanked on both sides by con-
fused mixture of rhyolite, tuff and
brecca. The rocks are all of a
whitish color and a little digging re-
vealed good ore near the surface.
The dyke as exposed occupies an al
most horizontal position, with slight
DIP to the southwest, and varies in
thickness from 60 to 70 feet, 1t
shows a distinct horizontal lamina-
ton and Is highly decomposed, CIV
ING little clue to its true nature. The
decomposition of the dyke resulted
in steotatc mass, white and pure,
and rarely stained with concentr1C
rings Of oxide of IRON. The straits
adjoining the dyke has been sub
jected to movements and displace
ments as shown by the breaks il
continuity and brecicated condition
of the rocks. This disruption witt
its attending fracturing and breccia
ton of country rock accompanied
by the movements of the dyke upon
itself, has proved suitable places TO
the accumulation of ore, the depo
sition of which was sequel to dyk
action, depending upon heated rock
for its effect.
The naturalization of the rhyolit
extends as far as known to dis
lance of 800 feet on either side 0
the dyke, carrying good value
through the entire mass. These va
ues consist chiefly of an alloy c
native gold and silver, the forme
predominating. The average prio
at the mint of metal taken from th
mines is from $12 to $14 per ounce
There is also q considerable amour
OF iron pyrites DISSEMINATED in
regular botryoidal masses, section
sometimes weighing several pounds
occurring along certain line
fracture, most Of which have di
solved out and left cavities only
Indicate their former presence. The
represent value of $4,000 per to-
Heretofore Thunder Mountain h
always been considered low graz
proposition, but discoveries MAJ
during the winter of 10000, al
the following summer 60 to she
The fallacy of this belief I.
dewey tunnel is in ore for sever
hundred feet with an average val
OF more than $96 to the ton, tappi
the deposit about 300 feet below t
outcrop of the dyke. But the ric
est ore met with, lies near the CO
tact of the dyke, as shown in t
"Caswell' tunnel, where specime
carrying beautiful crystals Of matt
gold and quarts are quite freque
Assays gave returns well In
thousands of dollars. Similar Of
are found near the hanging wall
the dyke. Through the courtesy
Mr.. Richie, 1 was shown here
contents Of several pans of dirt t.
en- Unfortunately from the upl
contact, their values ranging n