The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1907-10-07
fine GOLD IN
SAN JUAN RIVER
Prof. Arthur Lakes Discusses
Its Source and Cause
of FIGURING.
GROUND IN NATURES MILLS
PROCESS HAS BEEN IN OPERA
TON FOR AGES. ?
GROUND IN NATURES MILLS
arthur Lakes in Mining Reporter.)

(Arthur Lakes in Mining Reporter.)
Many more or less unsuccessful at
tempts have been made in southeastern
Utah to save the placer gold found by
panning along the stream, the complaint
being that the gold is too fine to readily
save. In a recent visit to the canyon OF
miles west of Bluff City, Utah, we had
an opportunity of studying the probable
origin of the gold. as well as the cause or
its extreme fineness.
The San Juan river drains portion of
what is known as the Grand Canyon dis
trict of the Colorado. The topography
and geology are characteristic of the
Grand Canyon. The prevailing rocks are
the red beds of the Jura-Trias composed
principally of COnglomerates, Sandstones
and q few limestones. Eruptive igneous
rocks are not specially characteristic, and
the river, in the area visited, had not, as
yet cut down to the basal granite.
Ieneous Rocks Scarce.
The few igneous rocks appearing above
the surface from small, isolated groups
of volcanic mountains of laccolithic origin
and structure, such as the Blue noun
tains, Sierra-el-Late or Ute mountain.
Sierra Carriso, Abajo and La Sal dotted
over the vast plateau. like few pimpies
on its ample surface. These volcanic islets,
although in some cases carrying copper
and other ores, have not proven, so far,
remarkable for gold deposits. Besides
these laccolithic mountains there are
few scattered dikes such as the Ship rock
and the Alhambra, the latter significantly
located on the crest of great anuclinal
fold which may indicate the presence be-
meath of a concealed laccolite. If we at
tribute gold deposits generally to igneous
rocks as an ultimate source then such
source is not characteristic OF this region
If the river derived its gold direct from
these few scattered igneous rocks, then
we might expect its gold to be more or
less coarse. especially in proximity to
them.
Source of Gold.
The source of the gold found in the bars
and bed of the river is more directly de-
rived from the erosion and disintegration
the Jura-Trias. These rocks are composed
largely of the detrftus of crystalline ig-
neous and metamorphic rock and may be
considered broadly as consolidated placers
in which the gold is fine and infinitely
though perhaps widely, disseminated. The
material of these rocks has all been
brought from considerable distance. and
from the wearing down and winnowing of
a former wide and thick continental mass
of which the extraordinary monuments,
castles and monoliths scattered ovey the
plateau are a striking evidence.
Ground In Natures Mill.
Any gold that these consolidated placers
may now contain must have passed
through cycle of milling. crushing, win
moving and sorting sufficient to have re-
duced ii to great pureness. even before
the consolidation of the rocks IN which it
occurs. And when il passed down by ero-
sion of the red beds into the torrent OF
the present stream its cOmminution was
completed in the tremendous natural mill
there at work. especially at certain sea-
sons. We had an opportunity of seeing
this mill in full action. Our camp was on
the edge of the canyon overlooking a spot
known as the 'Narr0WS &"
Owing to the rapid melting of the recent
SHOWS. the stream was on the rampage,
and was breaking off large portions of its
banks. SSpping the roots of the forest
trees and sweeping them down into its
embrace. Every now and then we would
hear in the canyon below a booming like
that of the rythmical breaking of great
ocean wave on the shore. and we would
see in the narrows a volume of reddish
muddy water pile up in mound on some
hidden obstruction or sand bank and roar
over 1t in a temporary waterfall; in
few minutes the obstruction appeared TO
be removed and the river rushed on
smoothly until few yards further down
or higher up the phenomenon was re-
peated-
Been Grinding for Ages.
The river was surcharged with sediment
derived from erosion of the red rocks and
appeared to plunge down and dig up its
bed and pile up, at intervals sand banks
formed and reforming them again lower
down or higher up. thus ever turning up
and pushing the material toward the Col
orado river. With such a ceaseless and
Powerful mill at work. night and day, it
was no wonder that any gold contained in
that terrible river would. on its bars and
banks. be Toured or comminuted TO its ul-
innate extent
We viewed hero not only the great mill
that for ages has been milling and com
minutlng whatever gold there might be-
but also the agent-the torrent choked
with sand-that as a great sand saw has
been saving down and planning off this
western plateau with no slight rapidity,
erodlng and corroding and deepening its
chine In action that has for ages cut up
that region into a labyrinth of canyons
and has removed from its surface prob
ably mile or more of vertical thickness
of rock, leaving behind a picturesque skel-
eton OF castles and monuments and mono
hths SO unique. strange, gigantic and
weird that IL is indeed the Wonderland
OF the West"