Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1903-01-31
Fissure Veins.

| fissure vein. d.
The highest authorities among geol-
ogists, however, are generally agreed
that fissure is simply a crack in the
earth's crust, which extends downward
at different anglesto great depth. This
definition, however, was not sufficiently
definite to satisfy the mining fraternity
and they have adopted terms which
qualify and describe the difference be-
tween these assures, so that now by Gus.
tom and common consent we have "for-
nation assures" contract assures" and
"true fissures." Those crevices in the
upturned states which traverse the for.
nation, and conform to the grain of the
rock, with slate walls on both sides, are
called formation assures. Those which
have walls differing in character are
called contract assures, while those
which cut across the formation are des
ignated as true assures.
But to fulfill the demand and be satis-
factory, they must in all cases be we'll
marked and defined and present the ap-
pearance of strength, depth and continu-
ity. AS distinguished from this class of
veins we haye "gash veins" s,""bed veins"
"hat veins" pocket veins" "lenticular
veins" and some others, but they do not
enter into our subject at this time.
The cause and origin of these fissure
cracks haye often been the subject of
discussion bet%esn miners. This con-
troversy is not between geologists; they
agree that these fissure cavities are (for
the most part) caused by the cooling and
consequent shrinking and folding of the
earth's crust. These cause wrinkles and
ridges all oyer the face Of the earth, and
are best exemplified by our mountain
ranges. Thus, we have the Allegheny
mountains on the east. and the Rocky
mountain ranges on the western side of
our continent. These mountain ranges
do not run parallel. There is no good
reason why they should, as in their for
nation they have simply followed the
lines of least resistance. tits reasonable
to suppose, however, that the formation
of these immense ridges would cause
fractures of the earth's crust and that
these assures cavities would extend
downward. into the earth to profound
depths. Nevertheless, there must be a
limit to the depth of these fssures, and
there are good and sufficient reasons why
it should be so. Chief among these is
that the temperature Of the earth in.
creases one degree for every fifty. five
feet of depth attained as we descend YER
tically into the earth. tits true that this
increa sc of heat varies in different places
| (from local causes), yet on the grand
average this is found to be true.
Figuring from this basis eminent geol.
ogists have calculated the. we would
reach point where water would boil at
depth of 1900 feet. 1t is considered
that the constant action of boiling water
upon the earth formation, together with
the pressure of the vast weight of rock
above, would prevent any marked tract
ure being maintained, for the reaso n
that the rocks would be in a semi-plastic
state. For this reason it is estimated
that all mining for metals must cease at
depth Of from two to three miles from
the surface of the earth. This, Of course,
is speculative, but natures laws are un-
varying, the reasons are good and the
premises are sound.
But this folding Of the earth's crust
does not alone account for all Of the deep
cracks and crevices which are classed as
fssure veins. Earthquakes and the up
heaval of the dikes of granite and por-
phyry, together with all of the intrusive
and igneous rocks, each and all have
played their part in producing what We
class as fissure veins. But we are too
fast in calling these veins. In the fore
going remarks we have only described
the cracks, crevices and cavities.
But cavity is not vein. To be such
it must be filed with mineral Of some
kind. In the performance of this feat
nature has employed many methods and
brought into play many forces. We have
not the space, even if We possessed the
ability, to enumerate and describe them
all. We can only make note of the most
prominent, and observe the conditions
as they are presented for our investiga-
ton. We can not fathom the causes
which haye produced these intricate and
stupendous results. We can only OBJ
serve tie facts which come within the
range of our senses, and from what we
have learned of the working Of the laws
of nature we formulate theory. And
by the aid of our reason we Judge of the
unseen from the seen, of the unknown
from the known, and he who reasons
best will come nearest the truth.
Men have bored into the earth some
thing over q mile, and our geologists
have measured the different strata and
made note of their relative position.
They have also investigated the forms oi
the earliest kind of vegetation from their
imprint in the rocks, and from the char.
acter Of that vegetation they judge ofthe
nature and climatic conditions of the
earth's surface at that remote age Of the
world. The fossil remains brought up
from the depths of the earth disclose the
fact of whether they belonged to the
denizens of the land or the sea. The
study of this subject has always been an
interesting one to me and my opinion il
based upon long experience and close
observation. This has been supplement
ed by reading the investigations of the