Iowa County democrat. [volume] (Mineral Point, Wis.) 1877-1938, 1905-07-06
IMPORTANT BULLETIN,
Zinc and Lead Deposits of South
western Wisconsin.

The zinc aud lead deposits OF south
western Wisconsin are described
briefly by Prof. u. s. Grant In Bulle-
lin 200 OF the United States Geological
Survey, which Is entitled "Contribu-
tions to Economic Geology, 1904" as
follows:
''This region comprises Grant, La.
fayette and Iowa counties. Ii lies
between the Wisconsin river on the
north, the Illinois boundary on the
south, and the Mississippi river on
the west. The principal towns are
Mineral Point, Platteville, Dodge
Vile, Darlington and Shullsburg,
which are connected by railway with
zinc smelters ut LaSalle, Peru aud
Wenona, Ill. Some OF the zinc Is
also smelted at North Chicago, and
most OF the zinc carbonates and the
lower grades OF the zinc sulphides are
shipped TO Mineral Point Wis. i,
where an extensive plant for the
manufacture of zinc oxide and sui
phuric acid Is located.
"The important deposits OF lead
and zinc occur In the Galena and
the surface rocks over the larger part
of the region. The Platteville lime
stone Is made up largely of non-mag-
ensian beds, although In It's lower
part there are certain magnetism
strata. The thickness Of the Platte
willie averages 30 feet, The Galena
limestone IL essentially u dolomite,
most OF which Is coarse-grained and
In, ha1p nan
from | foot TO feet In thickness.
''Thc oros consists OF galena, sphal-
erite, smithsonite and iron sulphide,
the last usually In the form Of mar
castle. The ore deposits occur I ~ in
cracks or irregular openings, (2l In
apparently breeciated or very porous
parts OF the Galona limestone, and
(3) In small particles In certain layers
of rock. The first are known as Gre
wise deposits, the second rs honey
comb deposits, and the third rs dis
seminated deposits, These three types
are frequently we'll defined, though at
some places they grade into one
another and cannot be regarded as
gesetically distinct.
"The crevice deposits are the most
important. In these the general order
OF deposition OF the ores was rs
follows, beginning next to the wall
rock; ~ marcasite; (2) sphalerite
with at times some galena; (3) sphal-
critic, frequently the main mass OF the
ore; ca cubes OF galena; 10y calcite;
(8) barite; ~ open cavity. Though
not universal this order Is very com.
mon. These ores lie below the level
OF ground water, In the crevices
above this level are layers Of smith.
sonitc derived from the alteration of
sphalcrite) and galena, the latter fire.
quently In large masses. Such ores
were early mined In this region and
are still mined, although they are now
of much less relative Importance than
formerly.
"ln former years, and today In
some of the smaller diggings, mining
was carried on In very primitive
manner for the most part. The ores
we're usually mined and brought to
the surface by hand, and cleaned by
cobhing or by hand jogging. The
present development OF the region Is
due In great part to the introduction
of improved methods OF mining and
of concentrating the ores. During
the last three years about thirty con-
centrating mills have been erected.
Prof. Grant says In conclusion tina,
there is good reason to believe tina,
the bodies of sphalerite below the
level OF ground water will last for
many years and that considerable
mining industry will be carried or
here. The present high prices OF lead
and spelter, coupled with the fact thai
the lower grades OF sulphide ores car