The Pioche weekly record. [volume] (Pioche, Nev.) 1877-1900, 1882-12-23
A NEW METHoD or sxpAaAqIse
MINERALS.


been effected mainly by taking advantage
Of differences, in density, structure or
capacity for being rendered magnetic by
cacnation while no use has been made
of the striking properties eyinced in diff
ferenees Of specific cohesive strength.
The separation Of minerals Of unequal
hardness, and BY reason Of their greater
or lezs susceptibility TO break down into
fragments Of different sizes is not possible
with the ordinary crushing or stamping
mill; but il is difierens when the mass is
thrown violently against a hard resisting
surface. in which case, II the velocity is
properly proportional, only the more
brittle substances are broken. In order
to obtain proper separation Of iron py-
rites and zinc blende German Engineer,
Rutzenbach, has been led to experiment
on the use Of Vapart's centrifugal breaker,
not only as a crusher, but as separting
machine. When this apparatus is driven
at 500 revolutions per minute, Jumps of
iron pyrites Of twenty to twenty-five
millimetres diameter are reduced partly
to dust and partly to grains Of | and II
millimetre; but when the velocity is re-
duced to 400 revolutions they are scarcely
touched. Blonde, which is OF inferior
hardness, is reduced to the finest
fine stuff at 500 revolutions, while at
400 it leaves the apparatus partly as dust
and partly Of grains OF 0.5 to 80 milli-
metres in diameter. Ii, therefore, mix
ture Of two minerals are treated at the
lower speed of 400 revolutions per min
ute, the pyrites are almost entirely un-
altered, while the blende, being very
finely reduced may be separated by
simple sitting process. In order to make
the process continuous in action the
crushed ore is passed through hopper
into drum sieve making 9 2-l0ths revo-
buttons to every 100 Of the mill, and d.
vided into three parts with holes of one,
two and three millimetres respectively.
The coarser stuff passes into second
drum with two divisions, having holes of
six and eight millimetres respectively,
which is driven at eight revolutions per
100 of those OF the crusher The size of
the sieve holes depends upon those of the
particles operated on, and it is important
that these shall be as nearly uniform as
possible. The operation may be carried
on, wet or dry; but in the latter case it
is essential that the material shall be as
free from moisture as possible, as the
powder, if damp with about four per
cent. of water,l binds and easily stops up
the sieve holes. The dust is also very
great Inconvenience, which, however,
may be remedied by the use of small jet
Of water.
The separation Of the two minerals is
not completely affected, as the ungles of
Of the grains of pyrites are apt to break
off even at moderate speeds Of the ma
chine, and to become mixed with the fine
blende; but it is sufficient for ordinary
commercial purposes. The economic
value is shown by the following calcula-
tion. Mixed ores with equal contents of
biende and pyrites, are worth at the ut
most about los. per ton, and are not east.
ly disposed of at that price; but when
subjected to the treatment described
above, the products are IL cwts. of pyri.
ties, with five per cent. of blende, worth
9s. Cd and cwts; of blende, worth 3ls.
Cd, or a total Of Ais. for the separated
products. Taking the cost of the raw
material at l0s., and the working cost at
3D., the profits on the process appears to
be 30s. 3p. per ton Of stuff treated. The
amount of material that can be crushed
in Vapart mill is about FIVE tons per
hour passed once through, SO that single
apparatus will be sufficient for even
very productive mine, as mixed ores of
this kind never forms more than a com.
paratively small portion of the total pro-
duce. [Londonilining Journal.
1t is stated that the coal inspector of