The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-12-03
Millions of Years.


Then followed a succession of ad-
vances and recessions of the seas
! through a period of millions of years,
with gradual increase in the amount
and variety of life, as recorded by fos-
sill remains in the rocks. The country
about here was sometimes above and
sometimes below the seas. We will
pass over this period without further
comment because it is of little interest
to our present story Finally about
100000 years ago, the oceans re-
treated permanently from this section
> and the present day mountains began
to form, accompanied by extensive out
bursts Of lava of the kind that you see
In Durant canyon on the way to Greg
son Springs. These lavas spread out
/ from volcanic vents that have been so
worn away and concealed by later
rocks that they are difficult to locate.
Soon after this period of vulcanism the
granite which forms the main rock
around Butte was intruded into the
| lava and other older rocks. A com
mon accompaniment of granite intru-
sion is heated waters and gases which
appear at the surface as hot springs
The springs at Gregson, Alhambra
Boulder and Pipestone are of this
! character. These heated waters are
given off by the cooling igneous rocks
for hundreds Of years after the imme-
diate surface Of the earth has cooled
to normal temperature. 1t Is these
hot waters that form veins. The hot
waters and vapors have the chemica,
power of dissolving mineral substances
through which they pass and these
dissolved mineral substances are re-
deposited as the waters rise toward
the surface, losing temperature and
pressure. The waters Will ascend
along any line Of weakness in the path
IN the crust of the earth and minerals
VIII consequently be deposited in anv
of these lines of weakness. AS these
lines of weakness are usually fissures
or cracks in fairly straight lines the
resulting mineral deposits are USUALLY
straight and relatively narrow and are
called veins. Besides actually demos.
ting in open spaces along these frac-
lures the mineralized waters are often
50 powerful chemically that thew eat
into the rocks adjacent to the fractures
and deposit minerals at considerable
distances from the fracture. Minera,
deposits thus formed by replacement
or the rocks are very common the
world over and they are the most i'm
portant kind here in Butte. The gran
lite here Is not always completely re-
placed by the vein materials so that
much of the ore mined in Butte still
shows more or less of the structure OF
the granite.
The. veins which we have in Butte
are therefore nothing more or less than
FOSSIL channels of hot springs, the hot
waters of which happened to carry IN
solution and subsequently depositeT
minerals of copper, silver and gold in
a sufficiently concentrated condition t.
pay for mining. All through this
granite area from Butte to Helena and
from Pipestone Springs to Deer Lodge
hot springs existed and veins were
formed, but sad experience has shown
that in not one out Of ten of these veins
were commercial quantities of metals
deposited. A vein may be big and
strong and persistent in lenGth and
depth, and yet not contrin material
which will pay to mine.
During the 100000 years which
have elapsed since the formation OF
the veins in this district many import
ant changes in topography have taken
place. At the time the veins were
formed tha oountr,, ala - ..a,- :.