The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-03-12
LEAD AND ZINC MINING
IN THEJ0PL|N DISTRICT
GEOLOGY, ORE DEPOSITS AND
MINERAL CONSTITUENTS
FOUND IN THE ORE.

<1iHC OicS III tHc Joplin bISlTlCly
the title of an Interesting pamphle
issued by the bureau of mines, fror
which the following extract is taken
Geology.
According to the United States geo
logical survey the rocks in which tn
ore bodies of the Joplin district occu
consist mainly Of sedimentary bed
which lie within the Mississippian an
everything Pennsylvania series, o
carboniferous age. The greater pro
portion Of these deposits occur in tn
Boone ebert Of the Mississippian ser
les. but at Miami, Okla, important or
bodies are found not only in tn,
Boone ebert but in the everything rock
OF the Chester group. These forma
tons consist Of limestones cherts, ant
dolomites. with lesser quantities o.
shale and "soapstone" The geological
succession of the rocks is simple, ant
the formations, though nearly flat
have general dip to the northwest
Relatively speaking, there has been
little disturbance throughout this area
either by faulting or lateral move
ment, the most noticeable disturb
ances or unconformties being between
the Pennsylvania and Mississippian
formations.
Ore observation-disclosures.
The lead and zinc ores are distrib-
nted throughout this area in rather
well defined blanket DIETER known as
sheet ground") deposits, or in runs"
or irregular deposits.
The sheet ground" deposits include
those ore bodies that lie between the
stratified layers of bedded cherts and
are in nearly horizontal position.
They vary in thickness from a frac-
ton of an inch to several inches, and
here and there contain cavities lined
with crystals Of lead and zinc miner
ais with minor amounts of iron sui
phides and other minerals. The ore
beds are to 20 feet thick and are far
more uniform in richness of mineral
content and are more reliable in lat
eral extent than the other forms of
deposits. Brecciation is relatively un-
important in these "sheet ground" de-
posits
The runs and irregular bodies
may be divided into two classes
those in fairly hard ground where lit
tie timbering is necessary and those
known as soft ground deposits, which
require timbering in nearly all the
drifts as mining advances. These ore
bodies are usually of an elongated
form and at times are Of considerable
length and thickness. A few are cir
cular or semi circular in shape and
are known as circle deposits. The So
called runs and the irregular ore bod
les are found at shalower depths than
deposits Of the sheet ground type and
are as a rule considerably richer in
mineral content, often containing
large pockets of nearly pure blende
and galena. These minerals are COM
monty found associated with a dark
cOlored secondary ebert as the main
filling material of fractures and cav
tiles.
The most important gangues in
which zinc blende and galena occur
are ebert and dolomite with minor
amounts Of limestone, shale, soap |
stone and mud In some of the de-
posts the ebert and dolomite are in
mixed, the zinc blende being
Embedded in a black secondary ebert
which serves to cement the gangue
with the blende ebert or flint is the
gangue material of the
ore deposits in the district, and can
De recognized in three different vari-
tiles. the white ebert, the blue to gray
Inert, and the black or secondary
'hert The blue ebert is known as {
I'VE flint and its occurrence Is usu- t
lily an indication of the presence of ,
'lende. The black variety, which has t
.lready been mentioned as filing s
ractures, cavities and the interstices /
Il the brecciated rock. is generally t
ound in the brecicated areas closely C
ssociated with sphalerite, or in places n
nth galena and as a cementing ma G
erial or matriX for the blue and white "
herts with zinc blende. The social f
q cotton rock which is a decOmposed
bert, Is often found in layers several v
lches thick near the surface or over D
ing the ore bodies. This dead white $
lint or cotton rock rs noticeable in f
ne roof of some of the sheet ground Ii
lines, where it usually has to be TAX b
n down as waste along with the ore r,
r has to be propped up with posts at W
'equent intervals n
AS regards the vertical distribution n,
the ores mined, the oxidized ores ST
zinc and lead generally occur above W
nd near the level of groundwater; m
Glow this level the sulphide of zinc Ia
scomes dominant, the proportion of ht
llena becoming less and that of iron in
llphides greater as the depth in of
eases. The zinc blende is seldom
und in the weathered zone for It be-
mes oxidized and generally takes in
e form of silicate or carbonate of pc
nc. as the result of the action of ga
rface waters. AS the general course dc