elliptical
area 200-300 yards across. These areas were divided into 30 ft. squares
or claims. Paths were left between the claims to the diggings. Stones
were first recovered from the weathered yellow ground. Gradually the
workings deepened, the roadways became steepsided ridges leading often
to landslides, when working became more and more costly. This led in
1888 to a consolidation of all the diamond mining properties in the
Kimberley district, largely through the efforts of Cecil J. Rhodes. The
resulting organization came to be known as the De Beer's Consolidated
Mines, Ltd. The De Beer's mines have an area of 40 acres, in
cross-section and had a depth of 1,500 ft. Thesepipes are filled with a
porphyrite, ultra-basic lava; the pipes, occur, in clusters .and mining
has revealed that they have been derived from a common fissure at depth
and the pipes are located in lines of fissure. The material of the pipe
has been divided into the 'yellow ground', the weathered and oxidized
zone of kimberlite breccia, and the 'blue ground', the unweathered part
running to 5,000 ft. depth, which weathers easily When exposed; and
the' hardebank'—compact and well preserved kimberlite. Conditions have
been found to vary in pipes due to difference in origin. Different
pipes also produced diamonds of different nature. All these pipe mines
(De Beer's) were closed down owing to market conditions in 1932, after
they had produced diamonds worth £90 millions. These mines started as
open pits and passed on at depth into modern underground mining by
means of shafts and drifts. The Kimberley mine was worked to a depth of
3,600 ft. and most of the work was done by natives. All mines in South
Africa were shut down in 1941 and only maintenance work was done. It
has been decided to abandon the old De Beer's mine which had not been
worked since 1908. Pumping was discontinued on May 16th, 1941, after
clearing all equipment from underground.
82
6B
