Mineral Point tribune. [volume] (Mineral Point, Wis.) 1854-1858, 1858-05-04

Il.
observe marked similarity between the
two deposits.
This idea is based upon actual facts.
The lead veins of Wisconsin. like those
of England, Germany and Spain, have a
uniform direction which is common 10 each
system, and which they maintain through
long districts.
They extend often horizontally mile or
more subject only to such ira nsient inter
ruptlons as are common 10 veins every
where.
The associate ores and veinstones (con.
per, zinc, iron haryto, Gale, spar, &c.,l
are arranged similarly to those of other
countries, generally in parallel bands or
combs
In following the veins downward they
expand and contract, or change their con.
tents. Sometimes shrinking so as scarce
/ ly TO leave trace, and again expanding
into unusual productiveness. This is par
hcnlarly the case wherever the rock
changes It's texture. In very close textur-
ed rock, destitute of open cracks and fis-
sures being always unfavorahle, while
rock with large open assures is usually
found to enrich the vein.
The lead veins of the West are first
found IN the Galena limestone, and rock
whose entire thickness is abou; 24O feet.
where it is most fully developed. They
descend nearly vertically in the upper
beds of that rock, carrying pure lead ores,
but in its lower beds Secome DETECTED
from their course, and from fiat and pitch
ing sheets accompanied by the ores Of
zinc, iron, copper, &C., as veinstones.
I
succeeds is abont 20 feet in thickness.
1t generally dispersses the veins where
they fret etrike il, but when followed in.
to II the veins again resume their usual
richness, with the veinstones found in the
lower beds of the formation above.
Next below this comes sandstone from
A TO Is feet thick, which usually cuts off
the veins though in few cases the vein
has been traced into it too much in.pover-
'shed to be worked with profit. This
sandstone his been reached only at Min
eral Point and few other localities.
Below this sandstone lies heavy bed
ded massive formation of limestone, abou,
$50 feet thick, physically well adapted to
the reception and retention of ores.
Into these two last named formations no
shaft has ever been sunk upon the veins
10 settle the doubts which now exist as TO
their downward condensitv.
That the veins should be interrupted in
their downward passage, and that they
should be very much Impoverished or
completely cut off by the interven,ions of
soft sandstone, is entirely in accordance
with the concurrent experience of all
veins which have been worked throuph
different rocks
Such an interruption, however, furnish
es no good ground for regarding this as
the termination Of the VEIN
1t is general law of metallic veins
that they are affected by the changes in
the rock through which they pass.
In Europe mines, veins have often been
worked through barren ground hundreds
of feet, where they were Gu, off bv an
unfavorable change IN the strata Soon
er or later favorable change is sure to
be met. If the vein is vigorously followed.
The effect of the Shelvy layers of the blue
limestone is to dwindle and disperse the
veins, but when they are passed and the
coarser and heavier bedded portion of
this formation is reached, the veins are
richly charged with ore.
NJ. DIR. La Beche, formerly director Of
the Geological Survey of Great Bririan
remarks upon this point, "tha. experience
has shown 10 the miner that the ores bo
seeks are more likely to be found amid
or against some rocks than others. though,
the fissures in which they are found ira.
we're several different kinds of rocks. In
Derbyshire for example, where the same
assure not only passes through the noun
tain limestone, but olso the sholes and
sandstones, that lead ore keeps general
ly, though not altogether to the limestone
series. Indeed, at one time, the opinion
of the Derbyshire miners was ,ha, the
veins did not travere the loads,one or
blacks'ones, so unproductive were they.
1t is now, however, we'll known that the
veIos pass through these rocks as well as
the lnnestones, the ores beiDg commonly
absent where the former constitute the
walls of the veins, It's contents in those
situations being composed of other miner
al substances.
Among the limestones themselves, some
are considered more favorable than others.
Though the veins are continued INFO GER
tain sholes and sandstones, all of which
have been equally open to solution. or
carnations of any kind, it is rare that
theSe portions OF The veins contain any ao-
preciable amount of ore' Regarding
the changes in the metallic contents Of
the Cornish veins, according to the char
at.er of the adjacent rock, Mr.. Carne OBJ
serves. that III Godolphin the veins were
rich where the slate was gray, but poor
where 1T was black
Nj. Fournet, speaking of the mines of
Upper Hungary says: that the copper
lodes are richest in fine clay states. that
III Saxony the silver ores follow the
Gneiss; and that in the Hertz metallic
ores follow the Graewacke limestone"
These statements show the general
opinion of the best Geologists ard most
expeienced miners as TO the effect os
changes Of rock npon vein with .ravers-
es different beds.
THEODORE PARKEa A SEcovD for