The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-08-29
FOR REFRACTORY ORES.
A New Method of Extracting
Precious Metals by
Roasting.
Found Feasible at a Public Test
Made in Oakland YeSter-
day.

A satisfactory test of the rapid and
cheap reduction of base ore by roasting
was made near Shell Mound, Oakland,
yesterday afternoon. 1t is new process
and this was the first public exhibition of
the working.of the plant.
The rapid.roasting process promises a
great saving of the product of the ores
and of the cost OF obtaining it.
The roasting is done during the passage
of the powdered ore through fiue 100
feet in length and with a fall of three
inches to the foot. 1t requires from four
to ten minutes for complete desulphur-
ization of the ores in its passage. Three
furnaces about thirty feet apart commune
cate with the fue, and the flames from
them are driven into it. Near each fur
mace there is also series of blow pipes
opening into the side of the flue and
directed downward. The direction of the
blast of compressed air from the first
series causes rotary motion of the small
particles being roasted while the situation
of the next series of blow-pipes on the
opposite side of the f1ue is such that the
rotary motion is there reversed, and so on,
causing thorough stirring up of the par
ticles in their downward passage.
So great is the heat obtained that the
most refractory ore is completely deoxi-
died and all the arsenic and other bases
removed, leaving free milling gold ore to
be collected from the tanks at the lower
end of the fue.
But one of the most advantageous
features of this process is that all the vola-
tized metals pass on and are carried by a
pipe into tank of water The water is
afterward drawn off and precipitated to
secure the different metals that passed into
it in gaseous state.
Yesterdays test was a particularly
severe one, as it was made with concen-
trates or sulphurets instead of ordinary
ore, supply of which did not arrive in
time. The ten tons of sulphurets used
were brought from the Amador Queen
mine several months ago. The test, how
ever, was very successful in demonstrating
the value of the method.
The ore is first dry-crushed and then
powdered to forty mesh or the fine
ness of ordinary dust when it is
ready to be fed into the top of the fue,
and is lined with fire-proof brick. Green
lakewood is used for fuel and 100 units OF
air is consumed with every one unit of
wood. The burning of the gases in the flue
saves more than one-half the fuel REQUIRED
for ordinary furnaces.
BY the new process ore may be roasted
at cost of less than 81 ton, and 80 to 95
per cent of the assay value obtained.
The plant near Shell Mound cost $20, 900.
and has capacity of 80 tons day. 1t
would, If located at mine, require fifteen
men, divided into three shifts, to run it..
Three cords of wood are sufficient for fifty
tons Of ore with this furnace.
1t is estimated that with free water and
oak or other green wood at So so a cord
gold and silver refractory ores can by this
method be worked at the mine from the
dump to base bullion for from 81 so to So a
ton, according to the character OF the ore
and the size of the plant. The plan OF the
apparatus was conceived about two years
ago by II. P. Holland of this City, who has
recently secured several patents on the
process.
Among the men who witnessed the test
were George Montgomery, capitalist of
Oakland; General John Hewston, founder
of what is now the Selby Smelling Works;