, 1900-02-27
A LESSON IN MINING
SECOND PAPER OF THE SERIES
CONTRIBUTED BY PROF.
FULTON.
Mineral Deposits-Advice to Pros
Save Them Disappointments and
Weary Months of Fruitless Work.

Save Them Disappointments ant
Weary Months of Fruitless Work.
Rocks may be divided into three
great groups. First, igneous or erup,
tive rocks or those formed by the agen.
cy of heat. Second, sedimentary rocks
of those formed by the agency of wa,
ter. Third, metamorphic rocks or
those formed from the first two groups
through the agency of pressure and
heat. In the first group we have rocks
like granite, porphyry, trachites, ba-
salts, etc. In the second group, rocks
like sandstone, limestone, conglomer-
ates, etc, and in the third group we
have rocks like marble, quartzite,
schist, gneisses, etc.
The metallic mineral deposits are as
ISOLATED mainly with the ~igneous
rocks, that is to say an areaOt may be
of sedimentary rock) into which igne-
II rocks have been intruded is much
the most favorable for the finding of
metallic minerals, especially gold and
silver. We have countless examples of
this, for instance at Leadville, where
the veins are closely associated with
igneous rocks, especially quartz por-
phyry: at Cripple Creek. where the
mineral is found with eruptive rocks,
like phonolites and many other prom
inent examples. This fact is true also
of copper, lead and zinc, etc. although
lead and zinc, not gold or silver bear
ing. are found as in Missouri and Kan
sas in limestones, which are not cut
by igneous rocks. Iron and copper are
found. especially iron, in the older met
amorphic rocks, the schists and gneiss-
es which have probably been derived
from old igneous rocks.
Coal, oil and gas are always found
in sedimentary rocks or rock derived
from them. There have been cases of
men drilling and hunting for coal and
oil in igneous rocks, of course with
negative results. These facts give
help and hints to the prospector. Wyo-
ming is undoubtedly a great field for
the prospector, but the prospecting
must be done in an intelligent way in
order to have any result. First, the
prospector must locate for himself an
area in which the general conditions
are favorable for the presence of min
eral, as outlined above. Let us suppose
he is looking for gold, silver, copper,
etc., naturally the mountains are the
most likely places because there erup-
tive rocks are most apt to be found.
When he has arrived at this place he
should still make a further choice of a
comparatively small area, say two or
three square miles, which looks favora-
BILE and then set out to explore this in
a most systematic manner. A great
guide to the p%rospector is the float
tered about. This is rock broken from
the vein by the action of the weather,
frost, ETC., rolling down the mountain
side or carried off to a distance from
the vein by water. Few scattered piec-
es of float would indicate that the lode
or vein from which 1t was derived may
be quite a distance OFF. Considerable
quantity of float in large pieces would
indicate that the vein is near at hand,
and so the condition under which the
float is found often offers clues to the
~prospector, which may be of aid to him
in locating the vein. Float is some
times absent, if the veins are very
hard, as quartz, for instance, and resist
breaking up. If the country is bare a
vein can be readily distinguished from
the surrounding or country rock by. its
appearance. If it is harder than the
country rock it will project above and
stand out; if softer, it can be traced
by d depression in the ground, often,
however, it may be buried by the drift
and soil or covered with slide rock, if
on a steep mountain side. Then the
location of the vein is a much more
difficult matter. Most veins or the
surface present a stained or rusty ap-
pearance, which is due to iron rust,
manganese, (f black, etc. This is
known as the gosson (f the honey
combed and has the appearance of be-
ing leached), outcrop, or iron hat"
When the vein is covered by slide
rock, pieces of red stained rock lying
around often indicate the nearness of
a vein.
The finding Of a vein, of course does
not necessarily lean the finding OF
something valuable. 1t must be borne
in mind that very likely most veins
found will carry no values. or such
small values as to be worthless.
When the float or vein is found, 1t
should be closely examined for value.
The minerals usually found were men
toned In last weeks paper, and the
prospectors should be familiar with
these before starting out.
The School of Mines of the universe
ty will be glad to aid anyone in becom-
ing familiar with the common miner
ais and rocks. Sometimes the decom-
position Of the minerals at the surface
sets the gold free and the value Ia
readily shown by panning some Of the
crushed material, but 1t must be borne
In mind that II this does not show any.
thing, the ore may still be valuable. 1r