APRIL 1, 1897 | 
WALTURE 
523 
forming a group by itself, or wandering about making friendly 
calls. 
The clothing in the compound is diverse and original. Some 
of the men are great dandies ; otheis think that in so hota 
climate a bright coloured pocket-handkerchief is as great a 
compliance with the requirements of civilisation as can be 
expected, 
They get very good wages, varying according to the work. 
The work is appreciated, and there are always more applicants 
than can be accepted. On entering, the restrictions to which 
they must submit are fully explained. and they are required to 
sign for three months at least, during which time they must not 
leave the compound or mine. A covered way and tunnel lead 
the workers underground to the down shaft, while those work- 
ing on the depositing floors go and come under guard. It is 
seldom that a man does not return, once he has lived the life 
in the compound; some come again and again for years, only 
leaving occasionally to spend accumulated savings. Some of 
the careful men contrive to save money. They carry it at 
intervals to Captain Dallas to keep for them. Occasionally 
they ask to look at their savings, which may amount to 30/. or 
40/., accumulated by driblets. They are ignorant of savings 
banks or interest, and are content if they see their own money 
in the original rags and papers in which it was handed in. 
Sometimes Captain Dallas will have as much as 1000/, of these 
savings in his care. On leaving, the men generally draw all 
their savings, and it is not uncommon for a grateful Kathir to 
press 2/. or 3/. on Captain Dallas in recognition of his trouble. 
They are astonished when their offerings are declined; still 
more so when it is explained that if they would put their 
savings in a bank, they would have a few extra pounds given to 
them for the privilege of taking care of it. Bank accounts are 
beyond them. The Kaffir, on demand, must behold his coins 
just as he handed them in, wrappings and all. 
So much then for the diamond mining industry of Kimberley 
as I found it on my visit in the early part of 1896. I trust 
I have made you realise something of the daily life of the 
diamond miners, of the skill and ingenuity with which their 
labours are controlled, and of the vicissitudes through which a 
diamond must pass before it is fit to blaze in a ring or a tiara. 
As for myself, I like to look back on our visit, and I am glad 
we made the journey. I like to recall the dusky natives at 
work and at play, with their smiling, good-natured faces. 
Tam glad to have seen that Arabian Nights vision, the strong 
room of the De Beers Company, literally heaped with stones 
won from the blue ground, purified, flashing, and of inestimable 
price, ready to play their part in the lives of men and women. 
And above all, I like to recall the friendly welcome, the 
thousand acts of kindness shown us by our able and enterprising 
colonial fellow countrymen. 
THE DIAMOND. 
I will briefly survey the chief chemical and physical charac- 
teristics of the diamond. I need scarcely say it is almost pure 
carbon, and is the hardest substance in nature. When heated 
in air or oxygen to a temperature varying from 760° to 875° C., 
according to its hardness, the diamond burns with production 
of carbonic acid. It leaves an extremely light ash, sometimes 
retaining the shape of the crystal, consisting of iron, lime, 
magnesia, silica, and titanium. In boart and carbonado, the 
amount of ash sometimes rises to 4 per cent., but in clear 
crystallised diamonds it is seldom higher than 0°05 per cent. 
By far the largest constituent of the ash is iron. 
The specific gravity of the diamond is from 3°514 to 3°518. 
For comparison, I give in tabular form the specific gravities of 
the different varieties of carbon :— 
Amorphous carbon ... 145 to 1°70 
Graphite... DET) 2a20 
Hard gas coke 2°356 
Boart o9 3°47 >». 3749 
Carbonado 3°50 
Diamond 3°514 5, 3°518 
The diamond erystallises in octahedra. It frequently occurs 
with curved faces and edges. Twin crystals (macles) are not 
uncommon. The crystals frequently contain microscopic 
cavities, and Brewster, by means of polarised light, found that 
the diamond round these cavities showed evidence of strain, as 
if from the presence of included gas at high pressure. 
Some crystals of diamonds have their surfaces beautifully 
NO. 1431, VOL. 55] 
And | 
marked with equilateral triangles, interlaced and of varying 
sizes. Under the microscope these markings appear as shallow 
depressions sharply cut out of the surrounding surface, and these 
depressions were supposed by Gustav Rose to indicate the 
probability that the diamonds had at some previous time been 
exposed to incipient combustion. Rose pointed out that 
similar triangular striations appeared on the surfaces of diamonds. 
burnt before the blowpipe. I have satisfied: myself that during 
combustion before the blowpipe, in the field of a microscope, 
the surface is etched with triangular markings very different 
in character from those naturally on crystals. The artificial 
Strize are much smaller and massed closer together, looking 
as if the diamond during combustion flaked away in triangular 
chips, while the markings natural to crystals appear as if pro- 
duced by the crystallising force as they were being built up. 
Many crystals of chemical compounds, alum, for instance, appear 
striated from both these causes. Geometrical markings can be 
produced by eroding the surface of a crystal with water, and 
they also occur naturally during crystallisation. 
Some diamonds have enclosed in their substance black un- 
crystallised particles of graphite. There also occur what may 
be considered intermediate forms between the well-crystallised 
diamond and graphite. These are ‘‘ boart ” and ‘‘ carbonado.” 
Boart is an imperfectly crystallised form of diamond, having no 
clear portions, therefore being useless for gems. Boart is 
frequently found in spherical globules, and may be of all colours. 
Being very hard it is used in rock-drilling, and, when crushed, 
for cutting and polishing other stones. Carbonado is the 
Brazilian term for a still less perfectly crystallised form of 
carbon. It is equally hard, and occurs in porous masses, and 
in massive black pebbles, sometimes weighing a couple or more 
ounces. 
Many diamonds after exposure for some time to the sun give 
out light when viewed in a dark room. Some diamonds are 
fluorescent, appearing milky in sunlight. In a vacuum, exposed 
to a high-tension current of electricity, diamonds phosphoresce 
of different colours. In these circumstances most South African 
diamonds shine with a bluish hight. Diamonds from “other 
localities shine with different colours, such as bright blue, apricot, 
pale blue, red, yellowish green, orange, and pale green. The 
most phosphorescent diamonds are those which are fluorescent 
in the sun. One beautiful green diamond in my collection, when 
phosphorescing in a good vacuum, gives almost as much light 
as a candle ; the light is pale green—almost white. 
During molecular bombardment the diamond becomes dis- 
coloured, and in course of time becomes black on the surface. 
Some diamonds blacken in the course of a few minutes, while 
others require an hour or more to discolour. This blackening is 
only superficial, and although no ordinary means of cleaning 
will remove the discolouration, it goes at once when the stone is 
polished with diamond powder. Ordinary oxidising reagents 
have little or no effect in restoring the colour. The black stain 
on the diamond is not due to a layer of amorphous carbon, but 
to graphite, which is much more resistent to oxidation. It is 
not necessary to expose the diamond in a vacuum to electrical 
excitement in order to produce a change. Some diamonds 
phosphoresce when exposed to the sun’s rays or to an electrical 
discharge in the air, and many more are phosphorescent when 
exposed to the Réntgen rays. In the latter case a slight super- 
ficial blackening also takes place. 
The diamond is remarkable in another respect. It is extremely 
transparent to the Rontgen rays, whereas highly refracting glass, 
used in imitation diamonds, is almost perfectly opaque to them. 
Texposed a flat plate of diamond, 0:0786 inch thick, and in shape 
a perfect equilateral triangle, side by side with a piece of glass 
of the same shape and thickness, over a photographic plate to 
the X-rays for a few seconds. On development the impression 
was found to be very feeble where the diamond obscured the 
rays, showing that most passed through, while the glass was 
seen to have obstructed all of them. 
By this means imitation diamonds and some other false gems 
can readily be identified and distinguished from the true gems. 
Diamonds occur in all shades, from deep yellow to pure white 
and jet black, from deep brown to light cinnamon, also green, 
blue, pink, yellow, orange, and opaque. : 
I have shown how interesting is Kimberley with reference to 
its buried diamond wealth. The enormous find and exportation 
of diamonds must bring reciprocal benefit ; and it would redound 
to our credit could we honourably do our part towards the 
pacification and development of the colony. 
