The Elk Mountain pilot., 1882-03-30
KIND on ORES WILL
CONCENTRATE.

S0&vA 4 xlI8 4 Ia
A correspondent in Colorado re-
quests Us to "explain IN 4 plain way
what constitutes an ore ofgold or silver
suitable for concentration" Like
most simple questions, this is not to
be completely answered in few words.
The art Of concentrating sres can not
be taught in an editorial paragraph;
and only those who understand the
theory and practice Of that art can
judge whether given ere may be
successfully concen.rated. Even such
persons, before actually decidipg this
question, need to study the locality
and the conditions, and probably also
to make some actual experiments on
the ore itself. If, therefore. We under
taketo state in plain words, and briefly
for the benefit of our correspondent,
the characteristics of ores suitable for
concentration, it must not be supposed
that we have exhausted the subject or
furnished an infallible guide of judg-
ment.
At the very beginning it should be
remembered, successful concentration
is to some extent a relative term.
Instances occur in which the valuable
and the worthless constituents of an
ore behaves so much alike under
mechanical treatment that they cannot
be separated at all. On the other
hand it seldom or never happens that
complete separation can be effected
by one operation. The general rule
is, that the attempt to get the "head-
ings" or concentrates free from worth
less material that is, to- make them
rich-throws more or less valuable
material into "tailings'' or "mid-
dlings;" while the attempt to obtain
tallings free from valuable material
leaves large amount of worthless
material in the other grades Of product.
Between these extremes there are many
degrees, much re-working of inter-
mediate grades and the final choice
of that combination of operations
which will give the largest net profit
is a matter OF no little difficulty.
The basis OF all mechanical separa-
tions Except magnetic separation, as
applied to some iron ores) is the
specific gravity of the minerals con-
taincd in the crude material treated.
particles of equal size and similar
shape, but of different specific gravity,
can be separated into classes accord
ing to their gravity; and this can be
done the more perfectly, the greater
is the difference in gravity. A heavy
mineral, like galena, for instance, can
be treadily separated from a gaugue
like quartz less readily from heavy
spar or zinc blende.
| All minerals, and particularly those
which yield a good deal of fine stuff
in crushing, must be classified as to
gravity; for the simple reason that
large piece ofa lighter material may
behave like smaller piece OF a heavier
mineral. Without going into the
mathematical explanation OF this fact,
it is sufficient to cite the we'll known
experience of gulch miners, who find
gold and the largest pebbles or boul-
ders Of quartz lying together at the
bottom Of the channel, on the bed
rock.
In the concentration of gold and
silver ores (though not in that alone,
another principle is involved. Not
only the gravity and the SIZE, but alse
the shape of mineral PARTICLES, deter
mine their behavior. Fine scales, for
instance, even of a mineral of high
specific gravity, will float or settle but
slowly in current of water, notwith-
standing their gravity, and hence may
be lost in the mass of worthless ma
terial, from which they might be ex-
pected, on the grounds of weight and
size alone, to separate themselves
&. H. Remtw.
Scene on D. & r. G.. sleeper, as
an old traveller is pouring his morning
dram from his flask. The dram proves
to be several ounces. The porter taps
\