Vernon County censor. [volume] (Viroqua, Wis.) 1865-1955, 1906-10-03

SuudI6-
When the days work is completed,
the pans, through each of which three
hundred loads have passed, are emp
tied or cleaned up and the concen.
trated deposits of diamonds, mingled
with other heavy but valueless miner
ais are then sent to the pulsator, whic
separates the diamonds sufficiently
for the sorting tables.
The work of picking out the dia.
monds by hand from the concentrate
on the sorting table was. of course,
slow and tedious. t was the only di-
vision of diamond mining and win.
ming which seemed beyond the appli-
cation of blind and unconscious ma
chinery. But men today are not in
clined to admit that anything greatly
worth doing is impossible.
A series OF experiments was initia-
ted by me with the object of separat.
ing the diamonds from the heavy val
Geless concentrates with which they
are associated. An ordinary shaking
or percussion table was constructed,
and every known means of separation
was tried with out success. One of the
employees of the De Beers. Fred Kris
ten was in charge OF the experimenting
under the supervision of the late
George Labram, the manager of the
large crushing plant and afterwofd
mechanical engineer to the company
Notwithstanding the fact that the
specific gravity of the diamond (352l
was less thar that of several of the
minerals associated with =, so that
its separation would seer a simple
matter, it was found in practice to Be
impossible owing to the slippery ma
ture of the diamond. The heavy con.
centrates carried diamonds, and dill
monds flowed away from the percGs-
sion tables with the tailings. When it
seemed that every resource to do
away with the head sorting had been
exhausted, Kristen asked to be allow.
ed to try to catch the diamonds by
placing a coat of thick grease on the
surface of the percussion table With
which the other experiments had been
made, Kristen had noticed that oily
substances, such as axle grease and
white or red lead, adhered to Ola.
monds when they CHANGED to come u
to contact, and he argued to himself,
II these substances adhered to dia
monds and not to other minerals in the
concentrates, why should not dia-
monds adhere to grease on the table.
and other minerals flow away? In this
way the remarkable discovery was
made that diamonds alone of a
minerals contained in the blue ground
will adhere to grease, and that all
others flow away as tailings over the
end of the percussion table with the
water. After this was determined by
thorough experiments, more suitable
shaking tables were constructed at
the company's workshops. These were
from time to time improved on. until
now all the sorting Except fir the very
coarse size) is done by these machines
whose power of distinction is far su
perior to the keenest eye of the ma
tive. Since the discovery of tn afinlt,
of grease for diamonds, experiment,
have been made with rubiees AMI
sapphires from Burma, and it WIS
found that grease caught these gem;
with th2 same certainty that it catch
es diamonds.
After thorough trial a number of
these unique Misunderstanding tables
tsee picturel were constructed ana
are now working on De Beers concen.
trates. Each shaking table is made of
corrugated cast-iron plates in five sec
tons, with a drop of about an inch
from one division to another. Thisk
grease is spread on the plates to cow
them on the top of the corrugations.
Strange to relate, the descending
diamonds stick on the face of the
grease, while ali other minerals pass
over it. Only about one-third of 1 per
cent Of diamonds is lost by the first
cable, and these are recovered almost
to a stone when the concentrates are
passed over the second table. The dis
elimination of this sorter is surrey
marvellous. Native workers, although
experienced in the handling of dia-
monds often pick out small crystals
Of zircon, or Dutch boart, by mistake;
but the senseless machine is practic-
ally unerring. 1t win catch rubies.
sapphires, and emeralds as well as dia-
monds, but. so far as it has been test
ed, 1t VIII not cling to anything but
precious stone. The grease which is
used loses its power to catch dia.
monds after a few hours work, owing
to its becoming more or less mixed
with particles of water. II is then
scraped off the tables. together WI 4
the diamonds adherirg to it, placed in
kettle made OF finely perforated
steel plates, and steamed The grease
passes away to tanks OF water. where
it is cooled and is again fit for use.
Formerly, of $4,000 loads, which IS
about the daily average of the guam.
tity washed at De Beers and Kimbar
ley mines, 16l cubic feet had to be
assorted by hand.
When the stones are cleaned they
are carefully assorted With reference
to size. color, and purity and made
up in parcels for sale. For several
years past the De Beers Company has
sold in advance it's annual production
to syndicate of London diamond
merchants who have representatives
IN, u a