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PRECIOUS STONES.
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105
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Diamond was there formed in the rock in situ at
the time of its consolidation from the molten condition, and that the
carbon was derived from the carbonaceous shales caught up in the molten
mass during its intrusion. C. von Leon-hard thought it arose as a
sublimation product. Liebig believed various products were formed, ever
growing richer in carbon, and from the final substances pure carbon
crystallised out as Diamond. Others held its formation to be due to the
decomposition of a gaseous hydrocarbon or of carbon dioxide. Simmler
suggested that carbon was soluble in carbon dioxide under great
temperature and pressure, deriving this idea seemingly from the
presence in Diamond of liquid carbon dioxide in minute cavities. St.
Clair Deville advocated an origin from halogen compounds of carbon.
Sorby felt that the presence of carbon dioxide in the cavities was
irreconcilable with the association of more than a very little water in
the formation.
Any
consideration of the subject must necessarily take into account the
modes of occurrence at the various localities, so it may be convenient
to briefly consider here where and under what conditions Diamond is
found.
By
far the most important locality at the present day is South Africa, for
this region now produces at least nine-tenths of the total output. The
discovery of Diamond there only took place in 18G7, and the exact
circumstances are variously given. According to the more general story,
the child of a Boer, named Jacobs, w:as seen playing with
some bright stone picked up in the neighbourhood. A visitor to the
house, named Schalk van Niekerk, saw it and offered to purchase it, as
it seemed peculiar to him, but his host insisted on making him a gift
of it. Van Niekerk, according
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