IMPROVEMENTS IN THE TREATMENT OF ORES AND MINERALS FOR THE EXTRACTION OF TIN
Year: 1868

page_text: LETTERS PATENT to Robert Oxland, of Compton Gifford, Plymouth,
in the County of Devon, for the Invention of "IMPROVEMENTS IN
THE TREATMENT OF ORES AND MINERALS FOR THE EXTRACTION OF TIN."
Scaled the 20th April 1869, and dated the 29th October 1868.
PROVISIONAL SPECIFICATION left by the said Robert Oxland at the
Office of the Commissioners of Patents, with his Petition, on the
29th October 1868.
I, ROBERT OXLAND, of Compton Gifford, Plymouth, in the County
of Devon, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE TREATMENT OF ORES AND MINERALS FOR THE EXTRACTION
OF TIN," to be as follows:-
This Invention has for its object improvements in the treatment of
ores and minerals for the extraction of tin. Hitherto the only methods
of treating tin ores has been by pulverizing with stamps or by the
ordinary Cornish crusher.

page_text: Now my Invention consists in the employment of grinding apparatus
in the manner hercin-after described.
1st. For reducing raw ores of tin to fine powder after they have been
partially pulverized by stamps or by a crusher.
And 2nd. For grinding burnt or calcined ores in such a manner as to
rub off the adhering oxide of iron and other impurities from the binoxide
of tin or black tin of the Cornish miner without pulverizing the black
tin more than can possibly be avoided.
I prefer to use a mill consisting of a cast-iron pan about 4 feet
diameter, and 2 feet deep, provided with a hollow central cone rising
from the bottom to the same height as the upper edge of the pan.
Through this conc is a perpendicular shaft which carries a runner sup-
porting a muller on which are fastened iron plates or shoes forming the
upper grinding surface which moves over a bed of cast-iron plates
fastened to the bottom of the pan. The perpendicular shaft is stepped
into a gland which rests upon a lever, the moving end of which is slung
with a rod so held with a nut and screw that the shaft may be easily
raised or depressed so as to regulate the distances of the grinding
surfaces. The pan is set on a frame so that the perpendicular shaft may
be driven from below by gearing at about seventy revolutions per minute.
The form of mill may be varied, but for the treatment of burnt or
calcined ores it is necessary that the rubbing or grinding parts should be
capable of being set to work at a suitable distance the one from the
other.
In dressing ores of tin, I proceed in the following manner: -I break
the ore either by hand spalling, or, preferably, by a crushing machine to
about a two inch cube. The ore is then hand picked for sorting purposes
and to remove waste, and it is reduced to a coarse powder by stamps or
a crusher; I then grind it to fine powder in a mill; preferably using the
apparatus already described, charging the pan with from 10 to 15 cwt. of
ore at a time and continuing the grinding with water until the whole is
reduced to an uniform pulp. When this is effected sufficient water is
added to make the pulp thin enough to run off from the pan into cisterns
provided for the purpose, from which the ore is: taken and subjected to a
series of washing operations until all the earthy matters are washed off,
leaving the black tin in combination with metallic sulphides and
arsenides and with wolfram in the condition known as witts. The witts
I calcine to remove the sulphur and arsenic, and to oxidize the metallic

page_text: bases. The calcined product after treatment with acid for the removal
of copper I I pass through the pan in the manner already described, but in
grinding I take care by the regulation of the distances of the grinding
surfaces to do no more than to rub sufficiently to allow of the washing
off the oxides without reducing the size of the particles of black tin.
This I ascertain by taking out samples from the pan from time or time
as the operation is proceeding and examining on the vanning shovel:
When sufficiently scrubbed the ore is removed from the pau as already
described and again subjected to washing operations for the removal of
remaining impuritics. If the ore now contains wolfram I treat with
soda ash as is well understood for the removal of the wolfram and after
washing off the loose oxides of iron and manganese I finally pass the
ore through the pan for the removal of the last traces of adhering
metallic oxides.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert Oxland in the Great Seal Patent Office
on the 29th April 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, ROBERT
OXLAND, of Compton Gifford, Plymouth, in the County of Devon, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of October, in the
year of our Lord One thousand eight hundred and sixty-eight, in the
thirty-second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Robert Oxland, Her special licence
that I, the said Robert Oxland, my executors, administrators, and assigns,
or such others as I, the said Robert Oxland, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend;
within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE TREATMENT OF ORES AND MINERALS FOR THE EXTRACTION OF TIN," upon

page_text: the condition (amongst others) that I, the said Robert Oxland, my
executors or administrators, by an instrument in writing under my,
or their, or one of their hands and scals, should particularly describe
and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the
Great Seal Patent Office within six' calendar months next and im-
mediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Robert Oxland, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof (that is to say) :-
This Invention has for its object improvements in the treatment of
ores and minerals for the extraction of tin. Hitherto the only methods
of treating tin ores has been by pulverising with stamps or by the
ordinary Cornish crusher.
Now my Invention consists in the employment of grinding apparatus
in the manner herein-after described.
First. For reducing raw ores of tin to fine powder after they have
been partially pulverised by stamps, or by a crusher.
And second. For grinding burnt or calcined ores in such a manner
as to rub off the adhering oxide of iron and other impurities from the
binoxide of tin, or black tin, of the. Cornish miner without pulverising
the black tin more than can possibly be avoided.
I prefer to use a mill consisting of a cast-iron pan about four feet
diameter, and two feet deep, provided with a hollow central cone rising
from the bottom to the same height as the upper edge of the pan.
Through this cone is a perpendicular shaft which carries a runner
supporting a muller, on which are fastened iron plates or shoes forming
the upper grinding surface, which moves over a bed of cast-iron plates
fastened to the bottom of the pan. The shoes of the muller are twelve
in number, leaving inch radial spaces or channels between each plate.
If the ore be ground in charges these spaces are left open, but if
ground in continuous stream of supply of ore and exit they are filled up
with hard wood on end grain to the grinding surface. The dies or
bottom plates on which the grinding is effected are four in number.
In each one are two channels, each about an inch wide on the top,

page_text: extending through three-fourths of the width so bevilled from the bottom
upwards that the end grain wood with which the channels are filled up
may be held firmly down. Each plate is sufficiently wide to fill up
the bottom of the pan, excepting a space of four inches between the inner
edge and the central cone and a space leaving a channel two inches wide
between the outer edge and the interior of the pan. Between each of
the four plates a space an inch wide is left which is also filled up with
hard wood, presenting the end grain to the grinding surface. At equal
distances on the inside of the pan are slots or channels for holding
three curved pieces of iron so fixed as to cause the throwing of the pulp.
from the circumference to the centre when the orc is ground in charges.
These pieces of iron are not required when the ore is ground by running
it in a stream of water into the centre of pan, and allowing it to pass
off as it comes through the mill. The perpendicular shaft is stepped
into a box gland containing a lenticular piece of hard steel on which
the end of the shaft rests and moves. The gland rests upon a lever;
the free end of which is slung with a rod so held with a nut and screw
that the shaft may be easily raised or depressed so as to regulate the
distances of the grinding surfaces from each other. The pan is set on a
cast-iron cylindrical frame having large holes in the side so arranged
that the perpendicular shaft may be driven from below by a belt on a
pulley attached to the shaft at about seventy revolutions per minute.
The perpendicular shaft is so fitted with a feather on it that it may
be raised or depressed through the horizontal pulley by which it is
driven, even while in motion. The form of mill may be varied, but
for the treatment of burnt or calcined ores it is essential that the rubbing
or grinding parts should be capable of being adjusted at a suitable
distance the one from the other.
The accompanying Drawing shew the structure and arrangement of
the mill..
In dressing ores of tin I proceed in the following manner :-I break
the ore cither by hand spalling, or, preferably, by a crushing machine,
to about a two-inch cube. The ore is then hand picked for sorting
purposes and to remove waste, and it is reduced to a coarse powder
by stamps or a crusher. I then grind it to fine powder in a mill
preferably using the apparatus already described charging the pan with
from 10 to 15 cwt. of ore at a time and continuing the grinding with

page_text: water until the whole is reduced to an uniform pulp. When this is
done sufficient water is added to make the pulp thin enough to run off
from the pan into cisterns provided for the purpose, from which the orc
is taken and subjected to a series of washing operations until all the
earthy matters are washed off leaving the black tin in combination with
metallic sulphides and arsenides and with wolfram in the condition known
as witts. The witts I calcine to remove the sulphur and arsenic, and to
oxidize the metallic bases. The calcined product after treatment with
acid for the removal of copper, I pass through the pan in the manner
already described, but in grinding I take care by the regulation of the
distances of the grinding surfaces to do no more than to rub sufficiently
to allow of the separation of the metallic oxides without reducing the
sides of the particles of black tin; this I ascertain by taking out samples
from the pan from time to time as the operation is proceeding and
examining them on the vanning shovel. When sufficiently scrubbed
the ore is removed from the pan as already described, and again
subjected to washing operations for the removal of remaining impurities.
(The products now obtained consist of black tin nearly pure, unless.
associated with wolfram and tailings.) If the black tin contain wolfram
I treat it with soda ash, as is well understood for the removal of the
wolfram, and after washing off the tungstate of soda and the loose
oxides of iron and manganese I finally pass the ore through the pan
for the removal of the last traces of adhering metallic oxides. For the
separation of any black tin remaining in the tailings I again grind them
in the pan and wash the ground product as before, repeating the
operation until all the tin is completely removed. I prefer repeatedly
passing the tailings through the pan to completely grinding them to an
impalpable pulp at once as I thereby avoid reducing the black tin any
more in size than can possibly be avoided. This is a matter of great
importance, as when the black tin is too finely ground it is liable to
be carried off in the stream of water used in the dressing operations. In
dressing calcined ores and "burnt leavings" if the ore be sufficiently
tender it may be advantageous to grind it by running it into the centre
of the pan in a stream of water, and as it passes out from between the
grinding surfaces adjusted by the movement of the perpendicular shaft
allowing it to run off either into "stripps" or into circular buddles,
whence any tailings required to be further ground may be returned to
the pan and ground as before.

page_text: I claim the treatment of ores and minerals for the extraction of tin
in the state of the binoxide of tin or black tin of the Cornish miner by
means of grinding apparatus in manner substantially as herein specified.
In witness whereof, I, the said Robert Oxland, have hereunto
set my hand and seal, this Twenty-seventh day of April, in the
year of our Lord One thousand eight hundred and sixty-nine.
ROBERT OXLAND. (L.s.)