520 
IA URE 
[Aprin I, 1897 
blue ground does not show any signs of passing through great 
heat, as the fragments in the breccia are not fused at the edges. 
The eruptive force was probably steam or water-gas, acting 
under great pressure, but at no high temperature. According 
to Mr. Dunn, in the Kimberley mine, at a depth of 120 feet, 
several small fresh-water shells were discovered in what appeared 
to be undisturbed material. 
The rock outside the pipes and encasing them is called ‘* reef.” 
Inside some of the mines occur large masses of “ floating reef,” 
covering an area of several thousand square feet. In the De 
Beers mine is what is called ‘‘the snake,” a dyke of igneous 
rock taking a serpentine course across the mine, and standing 
like a vein nearly vertical, varying in thickness from 2 to 7 feet. 
The areas of the mines are :— 
K mberley 33 acres 
De Beers : ‘ Et i) 225s 
Dutoitspan... : : Se45ine 
Bulfontein ae , Me me ve 3Oanee 
Before the discovery of the mines there was nothing in the 
superficial appearance of the ground to indicate the treasures 
below. Since the volcanic ducts were filled with the diaman- 
tiferous ground, denudation has planed the surface and the 
upper parts of the craters, and other ordinary signs of volcanic 
activity being smoothed away, the superficial and ubiquitous red 
sand covered the whole surface. The Kimberley mine seems 
to have presented a slight elevation above the surrounding flat 
country, while the sites of other mines were level or even 
slightly depressed. The Wesselton mine, within a mile of 
Dutoitspan, has only been discovered a few years. It showed a 
slight depression on the surface, which had been used as a shoot 
for dry rubbish. There are other diamantiferous pipes in the 
neighbourhood, but they are small, and donot contain stones in 
payable quantities. More recently another diamantiferous pipe 
has been discovered about forty miles off, near Klipdam, and is 
now worked as the Leicester mine. Other hoards of diamonds 
may also be near ; where there are no surface signs, and the 
pipe itself is hidden under 10 or 20 feet of recent deposits, it 
is impossible to prospect the entire country. Accident has 
hitherto been the chief factor in the discovery of diamond 
mines. 
How the great pipes were originally formed is hard to say. 
They were certainly not burst through in the ordinary manner 
of volcanic eruption, since the surrounding and enclosing walls 
show no signs of igneous action, and are not shattered or 
broken up even when touching the ‘‘ blue ground.” It is pretty 
certain these pipes were filled from below after they were 
pierced, and the diamonds were formed at some previous time 
and mixed with a mud volcano, together with all kinds of débris 
eroded from the rocks through which it erupted. The direction 
of flow is seen in the upturned edges of some of the strata of 
shale in the walls, although I was S unable to see any upturning 
in most parts of the walls of the De Beers mine at great 
depths. 
The Kimberley mine is filled for the first 70 or 8o feet with 
what is called ‘‘yellow ground,” and below that with ‘* blue 
ground.” This superposed yellow on blue is common to all 
the mines. The blue is the unaltered ground, and owes its 
colour chiefly to the presence of lower oxides of iron. When 
atmospheric influences have access to the iron it is peroxidised, 
and the ground assumes a yellow colour. The thickness of 
yellow earth in the mines is therefore a measure of the depth of 
penetration of air and moisture. The colour does not affect the 
yield of diamonds. 
The contents of the several pipes are not absolutely identical. 
The diamonds from each pipe differ in character, showing that 
the upflow was not simultaneous from one large reservoir below, 
but the result of several independent eruptions. Even in the 
same mine there are visible traces of more than one eruption. 
The blue ground varies in its yield of diamonds in different 
mines, but it is pretty constant in the same mine. In 1890, the 
yield per load of blue ground was— 
From the Kimberley mine from 1°25 to 1°5 carats. 
* DekBeersimines 5, “L200; ei-s2e, 
of Dutoitspan mine ., O'I7 ,, O'5 carat. 
»,  Bulfonteinmine ,, 075 ,,0°33 ‘‘ 
Both in Kimberley and De Beers the blue ground on the west 
side is poorer in diamonds than the blue ground in other parts 
of the mines. The diamonds from the west side also differ 
NO. 1431, VOL. 55] 
somewhat from those in other parts of the same mine. The 
diamonds from each mine have a distinctive character ; so 
uniform are the characteristics that an experienced buyer can 
tell at once the locality of any particular parcel of stones. De 
Beers and Kimberley mines are distinguished by the yield of 
large yellowish crystals. Dutoitspan yields mainly coloured 
stones, while Bulfontein—half a mile off—produces small white 
stones, occasionally speckled and flawed, but rarely coloured. 
The diamonds from the Wesselton mine are nearly all irregular 
in shape; a perfect crystal is rare, md most of the stones are 
white, few yellow. The diamonds from the Leicester mine 
have a frosted, etched appearance ; they are white, the crystal- 
lisation irregular (‘‘ cross-grained”’), and they are very hard. 
Stones from Jagersfontein, in the Orange Free State, display 
great purity of colour and brilliancy ; they have that so-called’ 
“steely” lustre characteristic of old Indian gems. Stones fronr 
this mine are worth nearly double those from Kimberley and 
De Beers. 
In the first days of diamond mining there was no idea that 
diamantiferous earth extended to any particular depth, and 
miners were allowed to dig holes at haphazard, and prospect 
where they liked. When the Kimberley mine was discovered, 
a new arrangement was made, and in July 1871 it was cut up: 
into about 500 claims, each 31 feet square, with spaces reserved 
for about fifteen roadways across the mine. No person at 
first could hold more than two claims—a rule afterwards 
modified. 
It may help to realise the enormous value of the Kimberley 
mine if I tell you that two claims, measuring together 62 by 
31 feet, and worked to a depth of 150 feet, yielded 28,000 
carats of diamonds. 
The roadways across the mine soon, however, became un- 
safe. Claims were sunk 100 or 200 feet each side of a road- 
way, and the temptation to undermine roadways was not always 
resisted. Falls of road frequently took place, followed by 
complete collapse, burying mine and claims in ruin. At that 
time there were probably 12,000 or 15,000 men at work in the 
mine, and then came the difficulty how to continue working 
the host of separate claims without interference with each 
other. 
The mine was now threatened in two other quarters. The 
removal of the blue ground took away the support from the 
walls of the pipe, and frequent falls of reef occurred, not only 
covering up valuable claims with rubbish, but endangering the 
lives of workers below. Moreover, as the workings deepened, 
water made its appearance, necessitating pumping. In 1878 
one quarter of the claims were covered by reef, and in 1879 
over 300,000/, were spent on removing reef and water. In 
1881 over 200,000/. were thus spent, and in 1882 more than half 
a million sterling was needed to defray the cost of reef re- 
moval. So matters went on until four million cubic yards of 
reef had been removed, at a cost of two millions sterling, and 
still little good was done, for out of 400 claims in the mine, 
only about 50 could be regularly worked. Ultimately, in 
November 1883, the biggest fall of reef on record took place, 
estimated at 250,000 cubic yards, surging half across the mine, 
where the bulk of it lies to this day. It became evident that 
open workings could not be carried on at such depths, and 
after many experiments the present system of underground 
working was devised. 
During this time of perplexity, individual miners who could 
easily have w orked one or two claims near the surface could 
not continue work in the face of harassing difficulties and heavy 
expenses. Thus the claims gradually changed hands, until the 
mine became the property first of a comparatively small number 
of capitalists, then of a smaller number of limited liability 
companies, until finally the whole of the mines have practically 
become the property of the ‘‘De Beers Consolidated Mines, 
Limited.” . 
UNDERGROUND WORKINGS. 
The system of underground working in use at the time ou 
my visit is as follows :—Shafts are sunk in the solid rock at a 
sufficient distance from the pipe to be quite safe against reef 
movements in the open mine. The main shaft at De Beers 
starts about 540 feet from the north side of the mine, and is. 
now over 1500 feet deep. Tunnels are driven from this shaft 
at different levels to cross the mine from west to east, about 
120 feet apart. These tunnels are connected with each other 
by two tunnels running north and south, one near the west side 
of the mine and one midway between it and the east margin 
