The Dalles times-mountaineer. [volume] (The Dalles, Or.) 1882-1904, 1898-04-16
JOHANNESBURG GOLD.
The City Built on the Precious
Metal.
Yet the Knowledge of the Assayist
Il Necessary, II IL Said, to De-
termine It's Exact Lo-
cation.

It Is comomnly 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 potassium.
| I reckon that one-third of the work.
able mines, possibly one-half, are now
shut down or unopened; but had it not
been for the MacArthur-Fo cyan
ide process-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 matter Of
chemistry. The visitor to mineralogi-
cal collection has seen specimens Of ore
with glittering flakes or crystal grains
Of the precious metal. A well-known
Canadian geologist was once taken to u
mine, and on the strength of the sheen
OF splendid ore on the side walls of the
mine passages he gave 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 Johannes
burg for miles without seeing a CLEAN
of what the miners call visible" 1t IL
the assayist who tells us there is gold,
and with refined modern methods he
can say exactly how much; but, so far,
it passes the wit of man to get it all
out. When lump Of ore is brought 10
the surface, if it contains any gold at
all it is rarely more than one grain in
10000, oftener one in $4,000. 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 finty cement. The rest Is
waste.
was pleased at the celdenhpis Deep
TO see that the Kafirs were intel i1cn<
enough to separate the wheat from lnc
chaff. The rough stone passed before
them on 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 1 =
other scintillation Of gold to guide
them. This done, the remaining ore is
crushed in steel mortars by metal
stamps or pestles weighing over 1000
pounds each. They pound the stone SO
exceedingly small that it flows out in
thin stream of muddy water through a
screen with meshes numbering 700 to
200 per square inch. Night and day these
ponderous stamps are grinding to this
minuteness quartz, pebbles, pyritic iron
and flinty cement that have for untold
or hr,r sa1
ing 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 mercury,
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 oiEc- half Is locked
in the embrace of pyritic iron and other
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 pre-
cipitate and attach themselves to zinc
shavings. Roughly speaking, the mer-
curry captures go per cent. of the gold.
~, and the cyanide 2s per cent.
There is still left in the shines 10 per
cent, more or less, unrecovered.
In the course of the year there
must be at least 6 a750,o00 worth
IF bullion thrown away on the
Witwatersrand. Treatment Of the
shines now in progress is saving Sac
ton of this amount. The Crown Reef
got 1892 ounces out Of the refuse last
but some of 1t will always be
ost. This waste Of man is nothing 70
the waste by nature. The reefs that re-
main are mere patch, probably, to
hose that once existed. They are what
$ left after ages Of denudation. But
.nough remains. Mr.. Rudd recently
tated that before the century was out
be Rand might be producing bullion
or 100000 soverdgns per annum.
Year as we are to 1900, the estimate Is
lot extravagant. When the rich deep
eveis get all 10 work the effect viii be
Telegraph.