Evening star., 1898-09-03
DIAMONDS IN SOUTH AFRICA.


Some Characteristic. About the Earth
In the Mines.
From Cassier's Magazine. o.
Regarding any reported discovery Of q
new diamond mine, one of the first ques-
tions asked is. els It a piper" because If SC
there is every reason to be assured of It's
permanency. These pipes are roughly
circular or ellipticaf in section, and several
hundred feet, sometimes one thousand feet
across. Contrary to the once common
belief, there is very seldom basin-like
depression or other change in the surface
topography to indicate their existence
The ground forming the top of the pipe
is, for about the first thirty yards in depth
usually of light yellow color, due to the
decomposition of the 'Kimberlite,' or dia-
mondiferous rock, and Is calleed yellow
ground" Blue ground" in which the Kim
berley and De Beers mines have been work
ing for years past, is the hard unoxidized
and unhydrated diamond-bearing rock. of
the general tone Of color indicated by its
name 1t requires drilling and blasting
like any other hard rock, but just the i'm
preston that diamonds are thereby crushed
and broken is erroneous. The fracture is
more often due to passage through the fine
rolls in the washing operations rather than
to blasting Upon exposure to air this rock
changes to a gray color, and disintegrates
and crumbles, especially after moistening
with water. 80.
To this fortunate characteristic is due
the existence of the extensive floors at
Kimberley, containing millions of tons OF
blue ground in all degrees of weathering.
The floors are divided up into spaces, 400
yards by 200 yards, and on these the blue
ground is deposited for depth of about
ten inches The only treatment to which
the fiat "veldt," or prairie land. is sub
tected previous to receiving the "kimber-
lite is to be stripped of grass, bush and
any loose stones Formerly it was rolled
hard and smooth, but this is not now done.
The first operation the Kimberlite under
goes is that of narrowing, the harrows be-
ing drawn back and forth between two
dred yards apart, thus avoiding the pack
ing that would take place If the blue
ground were travelled over by steam har-
row After proper interval. the next pro-
cess is that of winnowing. or collecting the
Jumps of hard blue" that will not disin-
tegrate into heaps. Portable tracks are
laid down and the Jumps are sent to the
erusher house.
if no rains have set in, the deposited
ground is wet by hose, complete system
of water pipe being laid over the floors
for the purpose.
After another interval, to allow of fur
ther weathering taking place. the material
is loaded into cars on movable tracks, run
to the main haulage and sent to the wash
ing machines. any ,remaining pieces of hard
blue being stacked separately and sent
to the crushing and concentrating mill.
The floor is then ready for a fresh deposit
from the mines. 10
The entire cycle of operations takes
about a year for the De Beers blue ground.
sometimes less than this when rains are
more frequent The Kimberley blue ground
disintegrates in half that time. The floors
are fenced about with barbed wire fencing.
watch being aided by a system of we'll
arranged arc lights.o II!
On July 1. 1897, thereo were lying upon
the depositing floors of the Kimberley, DE
Beers and the newly-started Wesselton
mine an amount of 2,576,694 loads of dia-
mond rock, equal to 2.061 355 tons. At a
moderate estimate sthis tonnage contains
over e., 100000 worth Off diamonds, and it
also represents "a Eeryr large amount of
capital invested in the mining and trans
portation of the material.