The Harrison times., 1900-07-07
GEOLOGY OF MINES.

lin district is of sedimentary origin
1t consists mainly of limestones,
shales, sandstOnes, cherts or flints
These occupy nearly horizontal po-
sitiOns, having been only lightly dis
turbed since they were deposited on
the bottom OF the ancient seas. The
general dip is toward the west, but
so slight as to be hardly preceptible
The country is crossed by many YER
teal fault planes, but the movement
has almost always been very slight,
usually a few inches at most, so that
they produced no tissure of any con-
sequence. They really amount to
nothing more than the common Joint
cracks to be seen in any deposit OF
limestone. These rocks belong to
the lower carboniferous epoch Oc-
casional small pockets of coal are
found in the shale. Almost all the
mineral deposits occur in the lime
stone and in the ebert.
The upper and lower limits of
the ore bodies are usually very
clearly marked by capping of bar
rem lime or ebert In a horizontal
rection the zinc and lead will thin
out without any change in the gan
que. Beyond the main body the gan
que will not always be entirely bar
rem, but small streamrs OF ore can
be trailed through it in all directions
from few inches to a knife blade in
thickness. These are not at all GER
tam to lead to another body. bat
they are about all the miner has to
guide him in looking tor new bodies.
In some cases pipes or chimneys
occur, but these are considered sim
ply as notifications of the general
massive form. A somewhat common
form is series of rough sheets or
layers of ore, alternating with lime
stone or flint. Distinct fssure veins
do not occur, the nearest approach
to these being the horizontal sheets
just mentioned. This is sometimes
called blanket formation, but the
name can be rightly applied only to
the country rock and not TO the ore
forma ton
In only few places does the min
eral outcrop at the surface, but it is
regularly found up to within ten
feet. The deepest shafts in the dis
trict are about 200 feet. while fully
80 per cent are less than $50 feet.
The ore bodies cut by these at the
various depths all have the same
general form and characteristics.
Although the ground has been
opened only to such slight depth, it
is known that the ore bodies contin-
ue to much greater depth, drill holes
have leen put down in all parts of
made BY different operators and in
widely separated places ag;ee as to
the existence of far richer and larger
deposits at 500 feet than those now
known above 200 feet.
The lead and zinc occur as sui
phides mainly. Blende or jack, the
sui phide of zinc furnishes almost all
of the zinc. Jack is found both mas
sive and in disseminated condition,
and in crystals. AS the latter, it is
found lining the cavities in the lime
stone which are so common.
Mixtures of gangue or vein stuffs
and minerals-metallife and
others-compose the ore deposits.
Although some shales and sandstones
heavy spar and clays, by far the
most common gangue materials are
flint and limestone, and of these two
flint is in the greatest abundance.
The ore bodies are masses of brec-
cia. The fragments are mainly flint
derived from the country rock.
Limestone is also often found. The
are always angular and
never water-worn The interstices
are filled with jack or galena, or both,
deposited from solutions. The flint
vary in size from that of pea to
several feet or more in diameter.
The sulphides are disseminated
through it, as they are through the
limestone. Zirc and lead both occur
also in irregular sheets or veins,
sometimes forming the cementing
material of the breccia
In places where the lime is not bad
ly broken up ore is found in seams
and pockets along the bedding
planes. When these widen out into
large chambers flint fragments begin
to come in. Calcite, borite, dolo-