Mohave County miner., 1900-09-29
Working Low Grade Lead Ores.

The following letter to the Engin.
eering and Mining Journal from the
lead mines of southeastern Missouri
shows what small percentage of lead
in ore can be worked at profit. OF
course the conditions are exceptionally
favorable, labor and supplies being
cheap in that locality and the market
close at hand. As an Offset for this the
leadbearing mines of Mohave county
are higher in grade and have the ad
vantage of gold and silver value. The
letter quoted says: In your recent
editorial on the Lead Mines of South
eastern Missouri" which is more gen
orally known as the Disseminated Lead
Belt from the unique character OF the
deposits, the statement is made that
the general average of the ore is "about
per cent Of galena concentrates that
average about GO per cent lead,
although some mills make products
ssssying as high as 70 per cent The
trict, and he begs to take issue with
this statement in justice to the excel
lent management of these properties,
as they have earned their dividends on
ores that average considerably less
than is stated in your editorial. For
assuming &c per cent lead As the aver
age assay of the concentrates, which is
rather high, as they frequently drop to
60 per cent, this would make the aver
age yield of the rock 4,66 per cent. in
metallic lead. which is entirely too
high for the average of this district.
To say what the exact average yield of
the rock amounts to Is difficult, as the
ore is constantly varying at all the
mines, and safe average can only be
deducted from the results of a long
period. As the ore Of this district is
found to vary, at least in small lots,
that reliable averages can only be Sc.
cured over long periods, aside from
the errors due to current practice in
arriving at the weights of the ore treat
ed and the concentrates obtained there.
from.
Rich bunches of ore are occas ionally
found in all the mines that may double
and even triple temporarily the usual
output of the mills, while bare spots
are encountered in all the deposits
that cut down the output quite as Sc
verely. It Is true that these violent
fluctuations in the output are only
temporary, and seldom extend ovel
long periods, but they are sufficient tc
enable authentic statements to be
made that the yield of the ore varie:
from to 10 per cent in daily runs
though both these figures are extremes
This variation IN the tenor of the ore
has resulted In the larger companies
changing their policy of trying to wiz
their entire outpnt from one or two
shafts by operating several shafts
which secured much more uniform re.
suits in output by mixing different
ores, as well as being able to favor the
ore bodies when in lean ground. This
policy has greatly reduced the great
fuctuation in the output in the earlier
career OF Shese properties, and has en-
abled them to be brought much nearer
a constant output or to "lead factory
basis. Taking the annual output OF
the different properties, it will bt
found that the yield of ore ranges from
3 to per cent in pig lead, or from AZ
to per cent in mineral, as the con
centrates are locally called, and NEAR
average for the entire district, If II
could be accurately obtained, would
probably show yield Of 3.3 to 3.5 pei
cent in pig lead to the ton of ore
broken. A yield Of over 3.5 per cent
lead is very satisfactory aud above the
average, while the good properties car
pay dividends on 3 per cent. basis
The minimum basis on which the roci
is broken and milled is usually taker
at 2 per cent, and while no money car
be made on this yield, yet large guam
titles of rock but little better than thi'
4 l. k.