Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1905-02-03
Zinc and Lead In Noi thwestern ILL.,
nois.

| An interesting and instructive pa
per entitled Zinc and Lead Deposit:
OF Northwestern Illinois has recently
been written by II. Foster Balm OF the
United States Geological surves. II
contains descriptions of the topo
graphy. geology. and ore deposits OF
northwestern Illinois. with a discus
sion a. 10 the origin of the deposits
and representations regarding the fu
ture development of the district. Zinc
and lead minerals are found in two
widely separated districts in Illinois
One OF these is in the extreme south
ern portion OF the state and the other
in the extreme northwestern part. The
principal ore of the southern district
Is fiuorspar. and the production of
lead Is merely incidental This dis
trict has never yielded zinc in CONNER
cial quantity. though small amounts
Of both blende and smithsonite have
been found at a number OF points.
The mines and prospects of north
western Illinois occur entirely in 10
Dayiess county. and the majority OF
them are found within a very few
miles of either Galena or Elizabeth.
j ais hlEtil'A pun vi
the upper Mississippi zinc and lead
field. which lies mainly in Wisconsin.
but includes parts OF Illinois and Iowa
The field. rs a whole. includes approx
mately 1000 square miles. In the
northwestern Illinois district. which
comprises some OF the richest parts of
the territory. ore is now being mined
or prospected for upon 90 10 % separ-
ate sections of land. The whole of 10
Daviess county may be considered.
with some probability. as within the
mineral field. .
I'm 1852 this region is estimated to
have produced $4,000 tons Of lead. an
amount equal 70 10 per cent Of the
worlds production and 81 per cent of
the American output of that year.
Lead mining in the region continued
To- be important up to the opening of
the rich silver lead mines OF the west
ern states in the early sixties. The
production then rapidly decreased. and
for some years IL has been unimpor-
tant. amounting only TO approximately
1000 tons year.
Since 1860 the district has made
steady shipments OF zinc ore. and in
certain years the Illinois mines have
contributed a notable portion of the
product. At an earlier period the car
Donates and silicates only were used
for spelter production but blende has
long been the main ore used for that
purpose. and lower and lower grades
OF sulphide ores are now finding buy
ers. Five years ago. the upper Mis-
sissippi mines produced zinc carbonate
principally, but now the main output
is blende. although carbonate is still
shipped. Relatively unimportant as is
the present production of the mines in
this area. il Is believed that in the
future this district will play a larger
role in supplying zinc furnaces.
The dominant topographic feature
of the region is an upland plain lying
about 500 feet above the sea in the
southern portion of the area and ris-
ing gently toward the north. The geo
logy. and the geologic history of the
region. which are notably simple. are
briefly discussed by Mr.. Balm. The
region is one of unmetamorphosed. |
little-disturbed. sedimentary rocks of
PaleoZoic age. and there are no igne-
Gus rocks in or near it. The more i'm |
portant minerals which enter into the |
composition OF the ores found in this
region are also listed by Mr.. Balm and |
their characters noted.
The ores OF this region may be class
ed as galena or lead ores. smithsonite |
or zinc carbonate ores. and blende or
zinc sulphide ores. The galena or
lead ores are characteristic of the up
per horizons and are those which at
tracted attention in the early eXploita-I
ton of the region. Despite the many
years of careful prospecting since the
district was first opened. small quaint
ties of these ores are still found and
mined. Somewhat below the lead ores
proper il the zone or zinc-carbonate
ores from which. in the years 1860
To 1890. the main ores OF the region
were obtained. As usually prepared
these ores carry from 30 10 40 per
cent OF metallic zinc. Below the zone
Of zinc-carbonate ores is a zone in
which blende becomes dominant. As
sociated with the blende are Gaiena
and the sulphides of iron. The ores
low most worked at the mines are the
zinc sulphides. which require the cree
ion of much more elaborate plants
han are necessary for the reduction
II the other ores. This takes more
,apital and results in the concentra-'
ion OF effort upon q smaller number
If veins.
Mr.. Rain devotes considerable space
o a description of the miles OF occur
ence of these ores They occur in
What have long been known locally as
crevices" but are sometimes termed ,
cash veins" which are considered
Intermediate in character between reg
egated and true veins In the crew
ces and openings the characteristic