Gilpin observer., 1901-07-25
PINE CREEK VEINS.
Report Made by Professor Arthur Lake
on Geology of Michigan Hill and
Its Veins

Arthur Lake on the geology OF Michigan
hill, at Pine Creek, on which are located
the famous group of minss owned by
Judge Paris r. Hiatt; also a statement
by DR.. Pearce, of the Boston g. Colorado
Smelling company, as regards tellurium
ore:
"The mass of foundation rock of the
the hill is of granite type known as
gness and schist. The upper 800 feet or
cap of the northern section OF the hill is
composed of loose blocks OF eruptive
igneous porphyritic rock, the loose
blocks lying one on another probably to
a considerable depth. There are two or
three varieties of eruptiue rock; the most
prominent seems to be porphyrite, a
lava or igneous rock related to andesite,
and diorite containing locally fragments
of dark hornblendic rock, probably
torn from the mouth of the assures in
the mountain through which the por-
phyry assembled, which is now filled by a
dyke or dykes of solid lava, cs seen in
the Rob Roy tunnel.
"This dixie may have been connected
with an intrusive sheet or laccolte at
the tsp, now represented by erosion at
the summit of the hill.
"The opposite or southern peak of the
hill is OF bedded gneiss and schist,
HATS gulch specifically dividing the
volcanic area from the granitic. The
geology OF both sections of the hill, par
ticularly the northern or volcanic one, is
quite favorable to vein and ore occur
rences.
"The character of the eruptive rock,
though not identical with the andesite
OF Cripple Creek, is nearly allied to it,
and the huorine stains in the vein mat
ter, together with the geodes Of opaline
and chalcedonic quartz, show that
solfataric vapors and springs were
present after the eruption, favorable to
the forming OF veins and the depositing
of ores. Moreover, there is reason to
think this part of the mountains is a net
work of fissure veins.
The first surface indications of veins
on ascending the hill are found in nu-
merous fragments Of good looking quartz
float, often stained with purple fuorine,
and often honeycombed and oxidized
This float is also characterized by cavi-
ties lined with opaline or chalcedonic
quartz, s,gether with crystals OF smoky
quart:s The float is sometimes yellow
like jasper. This float appears to be
scattered all over the hill sido, and in
many cases indicates the presence of
some veins.
THE Rob Roy tunnel is 1900 feet above
the Hiatt tunnel at the creek and 900
feet below the great fissure or crater.
The vein is true fissure between walls
OF porphyrite which is dixie. Direc-
tion Of the vein is east and west, little
north of east. The tunnel is 175 feet
deep. The vein between walls is of
quartzose, gangue and porphyry, show
ing a cleavage structure parallel to the
walls, as il a zone OF shearage, like some
Of the veins nt Cripple Creek. The walls
on both sides, Of porphyrite, are we'll de-
fined and more or less smooth.
There are four cross veins. At tho
junction or crossing OF veins it is not un-
common to find large bodies of ore. An
improvement 10 the veins may also be
expected as they approach the center of
eruption. The latter doubtless had
good deal to do with vein and ore origin
Of the hill.
1.-The property is geologically quito
favorable to ore deposits, as shown by
the presence of both eruptive and
granatic rocks, and numerous veins.
The principal vein, the Rob Roy, is
good looking vein, with all tho accepted
attributes of a ilssure vein. We
may also reasonably believe the hill to
be network of veirs carrying more or
less ore. | would sugg t the outlay of
few thousa nd dollars to extend in
depth the present workings. There is
no saying what some OF the numerous
veins, or the Rob Roy itself, mny pro
duce with reasonable depth.
Statement oi Dr. rcnrce, boston Smelling
Company.
Telluride proper are rarely found to
exist near the surface OF lodes that may
contain them in depth. This is due to
he fret that tcllurium is susceptible TO
oxidizing action like iron pyrites and
other minerals when they are exposed
TO wcathering inAuenc y This weather.
ing notion, in the g q u tclurides, has
the effect of converting the te'lurium
into an oxidiaed form. which combin
he oxide Of iron and dom shows any