The silver messenger. (Challis, Idaho) 1890-1912, 1899-11-14
BENEFITS OF CONCENTRATION.
An Important Branch of MetaIIurgy That
is Sometimes Overlooked.

An Important Branch of MetaIIurgy That
Is Sometimes Overlooked.
One OF the most important branches
IN the me%tallurgical field of the min
ing Industry is that of concentration.
In many districts too little attention is
pald 10 It. Ores are shipped in bulk.
or are rudely hand-sorted and the best
portion shipped TO the smelters at a
profit, II Is true. but mt a greater cost
than would be necessary if concentra-
ton by mechanical means were first
employed. The second grade ores re-
main on the dump in many cases. prac-
tically waste, though containing good
values. In some mines the ores are
so disseminated through the gangue
that hand sorting can be carried on
rapidly and economically, but this is
MY the case where the ore occurs in
considerable masses. Hand sorting is
not economically practicable when the
mineral occurs in the form of dissent.
mated grains.
concentrating machinery is designed
for specific purposes, but has consider
able range of application. Most ores
are easily concentrated at low cost. but
some complex ores, such as those con
tanning an intimate mixture of pyrite.
galena and blende,. afford unsatisfac-
tory results. Fortunately, the latter
class of ores do not occur universally.
though found in large quantity in some
mining regions. Generally q plant
consisting of rock breakers. rolls.
trommels, jigs and concentrating ia
bles, buddles or belt machines are bet
ter adapted TO concentrating ores than
stamps and concentrating machines
alone, Tor the reason that IA large per-
centage of the mineral is obtained
IN the first parts of the operation, the
particles being comparatively coarse.
the fine material being collected in the
latter part of the process. STAMPS
rush all portions so fine that the sub
sequent recovery of the smallest par
ticles. which in some ores crushed by
stamps form the largest portion of the
valuable mineral. becomes a matter of
great difficulty. Rolls create a more
uniform product, as they have a ten
dency to crack and not to grind the
ore; and as most sulphide minerals
break along the lines of their natural
cleavage when subjected to crushing
force. the small grains have angular
faces which seem to facilitate their
separation from the gangue. 1t is the
aim of the successful concentration to
make as few shines as possible.
When ores high grade enough to ship
without sorting are concentrated by
machinery, the gangue, if containing
values in gold and silver. MAJ be sepa-
rately treated subsequently by ANAL
gamation or some teaching process. If
they will not pay for this subsequent
manipulation they certainly will not
pay the transportation and reduction
charges when shipped to the smelter.
II is a mistake which many miners
make TO send poor ore with rich. even
though the average be high. for if the
poor alone will not pay. it pays no bet
ter when mingled with the high-grade
ore. This is a simple proposition which
seems to be lost sight of il the desire
to secure quantity. In shipping ores
the aim should be to get as high value
as possible in as small bulk as posi-
ble.-Mining and Scientific Press.