Gilpin observer., 1900-01-18
ORE CONCENTRATION.
Various Phases of the Process Carefully
Considered.

Various Phases of the Process Carefully
Considered.
A Colorado mill man, speaking of the
low grade ores of that state, such as
are found in Boulder and Gilpin
counties, says that in his opinion no
improvement over existing methods
employed in the district are needed
Concentrating" he says in the Ward
Miner, ito make clean product, re-
,gardless of making II close saving, Sc
cures all the values that can be easily
and cheaply had by concentration, and
the use of cynide for the final treat
ment will in nearly all cases get from
ninety-five to ninety-nine per cent of
the values. Clean concentrates are a
very desirable product for the smelt-
ers, and l have no doubt they will do
all they can to encourage this system
OF milling. There is no excuse now for
any good and well located concentrat-
ing mill to stand idle. The addition of
cyanide plant fills the missing link.
We have made very extensive tests
on this line here in Boulder county,
and always with first-class results. 1t
is very safe to say that any method
that will handle Boulder county ore
will answer for any other ores pro-
duced in this state. Our tests show
shot WIN IL
ing mill and cyanide plant of fifty tons
per day capacity w-grade ore can be
converted into money at an expense
not exceeding $1.5U per ton. In the
two operations of concentrating and
cyaniding nearly full assay value is
saved. This S1.50 per ton will include
the expense of shipping and smelling
charges on the concentrates
In some ores the heavy sulphide ma
terial does not carry the highest value,
the gangue being richer than the con-
centrates, but such instances are COM
paratively rare. There are mines. too,
wherein are found both high-gr and
low-grade sulphides, and unless these
can be distinguished and separated in
the mine the lowgrade material will be
saved on the concentrators together
with the high-grade, reducing the aver
age value. If the lower grade sulphide
contains sufficient value to pay for
treatment at the mine. or for treatment
at the smelters. it makes no difference.
but, not containing such value. the low
grade material should be separated. if
possible, from that containing the high
grade. Where there are two clearly
recognized classes of ore occurring i'll
mine each of different character and
value, and where each can be easily
mined separately their treatment in
separate batteries would give better re-
suits than if these ores of differing ma
terial or value We're mixed and worked
together.
There are. however. few mines where
the ores, having sufficient value to pay
for the cost of mining and milling. and
containing sulphides as well, do not
justify concentration, and - in the
ur rrIn,hnr Of t1,n II
phides contain higher value than an
equal weight of gangue. clean concen-
tration is desirable, for the reason tina,
an admiXture of the relatively worth
less sands reduces the grade of the con-
centrates, and transportation and re-
duction charges have to be paid on n
quantity of material containing no val
lie, or at least value below the cost
of transportation and treatment.
1t is true, concentration may be car
ried mechanically beyond the limit of
economy. and when the point is reach
ed where closer concentration does not
result in profit it should cease.
Sorting by hand Is Il rude concentra-
riOn and should be regulated by the re-
suit. If the silicious portion is suscep-
tible to profitable treatment at the
lnine 1t should not be sent to the smell
and treatment is higher. On the other
hand, II the cost of more closely hand
sorting this ore is greater than the cost
of transportation and smelling, then
close hand sorting should be discontin-
ued. 1t often occurs that the gangue
remaining In hand-sOrted ore, which
might be treated at the mine at profit.
does not contain sufficient value to pay
for shipment and treatment charges,
which makes the situation still worse;
but the fact that such gangue does
contain sufficient value to pay these
charges and possibly leave profit does
not Justify its shipment when 1t may be
hand-sorted and treated at the mine
with greater profit
At most mines where hand sorting is
practiced the ore Is broken down with
hammers by a number of cheap men,
who labOriOusly break and almost me-
chanically separate the high grade sui
phides from the gangue. Necessar-
lily this process. unless carried to an
extreme and expensive point. leaves n
large amount of ore in the selected ore
sacked for shipment. 1t Is cheaper,
and will afford much more satisfactory
results, to run the ore through II break
er and, If necessary, through set OF
rolls.
Ore In which the high values occur in
punches or ribbons of sulphide mate
rial In ganguc of quartz. calcite.
baryta or other material may usually
be cheaply hand-sortet, as suggested
above. When the ore Is first brought
from the mine II should he dumped
onto fiat grizzly made of railroad
iron or heavy bars set half inch apart.
The ore should be washed by n stream
of water from II hose, the fine material
passing through the grizzly into II box
or bin beneath. The large masses, now
being clean. may be picked over by
hand and often n quantity OF clean
sulphide mineral obtained. while
rough breaking with II hammer will
nflpu rnsuli In the rncnYnrY of sllll