The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1897-08-10
HOW GOLD is GOT AT JOHANNES
BURG.


+ is commonly said that Johannes
burg is built on gold; it might be as
truly said that it is built on science, or,
in the concrete, on cyanide of POTASH
um Ireckon that one third Of the work.
able mines, possibly onehalf, are now
shut down or unopened; but had it
not been for the Macarthur Forest
cyanide prccess-discovered just ten
years ago-50 per cent. of the workings
still open would be closed. From first
to last the extraction of gold is a
matter Of chemistry. The visitor to
a meteorological collection has seen
specimens of ore with glittering fakes
or crystal grains Of the precious metal.
A well known Canadian geologist was
once taken to mine, and on the
strength of the sheen of splendid ore on
the side walls of the mine passages he
gave a certificate of the richness of the
workings. The sparkling nuggets had
been placed there and the renoWn of
the professor suffered somewhat. You
may traverse the underground ways of
Johannesburg for miles without seeing
a CLEAN of what the miners call wish
BILE" 1t is the assayist who tells us
there is gold, and with refined modern
methods he can say exactly how much;
but, so far, 1T passes the wit Of man to
get it all out. When a lump of ore is
brought to the surface, If 1t contains
any gold at all 1t is rarely more than
one grain in twenty thousand, oftener
one in fifty thousand. The first thing
to determine is whether there is any
likelihood of any of the metal. For this
purpose there has lately come into
pretty general use the sorting process.
What is wanted is the conglomerate,
the rock, known as reef, With quartz
pebbles and fiinty cement The rest is
waste
| was pleased at the Geldenhuis Deep
to see that the Kaffirs were intelligent
enough to separate the wheat from the
chaff The rough stone passed before
them on a revolving table, and they
could at once distinguish by inspection
the Jumps of quartz or sandstone that
were no good; though, as ] have said,
there Is not from one weeks end to an
other scintillation of gold to guide
them. This done, the remaining ore is
crushed in steel mortars by metal
stamps or pestles weighing over one
thousand pounds each They pound
the stone so exceedingly small that it
flows out In a thin stream of muddy
water through a screen with meshes
numbering seven to nine hundred per
square inch. Night and day these pom
derous stamps are grinding to this mi
nuteness quartz, pebbles, pyritic iron
and flinty cement that have for untold
ages been buried like misers embracing
their treasure deep In the rocks. All
the rest is pure chemistry. The soapy
looking water flows over copper plates
faced with quicksilver Man himself is
not more eager than this element to
clutch the precious metal, and before
the liquid has flowed foot the mercury
has laid hold of all the free gold. The
two form an amalgam, and the mercu-
ry, being easily retorted off by heat,
can be used again and again But the
mercury has taken out only about one
half the gold. The other half is locked
in the embrace of pyritic iron and 9TH
er base materials and from these it is
set free by the use of chlorine gas,
which has an affinity for gold and the
cyanide of potassium, which causes the
grains of metal floating in the solution
to precipitate and attach themselves to
zinc shavings. Roughly speaking, the
mercury captures fifty per cent. of the
gold, chlorine twelve, and the cyanide
twenty-eight per cent. There is still
left in the shines ten per cent, more or
less, uncovered.
In the course of the year there must
be at least three-quarters of million
sterling worth of bullion thrown away
on the Witwatersrand. Treatment of
the shines now in progress is saving a
fraction of this amount The Grown
Reef got 1,192 ounces out of the refuse
last month, but some of it will always
be lost. This waste of man is nothing
! to the waste by nature. The reefs that
remain are mere patch, probably, to
those that once existed. They are what
Is left after ages of denudation. But
enough remains. Mr.. Rudd recently
stated that before the century was out
the Rand might be producing bullion
for twenty million sovereigns per an
mum. Near as we are to 1900 the esti-
mate is not extravagant. When the
rich deep levels get all to work the ef-
feet will be enormous.-London Tele-
graph.