♦ I ♦
itH the growing mechanization characteristic
of nineteenth-century industry it was inevitable that, even before the
diamond era in South Africa had begun, the foundations should have been
laid for the exploitation for industrial purposes of the property of
the diamond as the hardest natural subÂstance known to man. Apart from
the use of diamond powder in the actual cutting of the diamond itself,
there developed the exploitation of the diamond as a drilling and
cutting instrument, an exploitation which scored a resounding triumph
when the first rotary diamond drill invented by Rudolph Leschot was
used in the driving of the Mont Cenis Tunnel in 1864. By 1927, a
leading U.S.A. technical annual summed up the then position as follows:1
Although
the diamond is best known as a gem, it has many important uses in
industry, and it is estimated that about 40 per cent of the output is
used for industrial purposes; this includes not only those special
forms of diamond, carbonado, bort2 and ballas, none of which
are suitable for gem purposes, but also a considerable quantity of
small low-grade gem stones. The various uses include glass cutters,
rock drill bits, wire-drawing dies, tools for highly accurate machining
of metals, tools for cutting vulcanite, or hard rubber, tools for
truing grinding wheels, tools for sawing rock etc.
Although all gem stones could be
used for industrial purposes, given their natural quality of hardness,
not all classes of industrial diamonds are suitable for all purposes
for which gem stones are used. There is therefore a margin of overlap,
those classes of industrials which could be used for gem purposes being
known in the nomenclature of the gem-stone industry as 'common goods'.
The margin of overlap is a shifting one: a general rise in the price of
gem stones will encourage the diversion of common goods from industrial
purposes, a fall will, if conditions in the industrial field are
favourable, push the use of common goods in that direction. There was,
and is also, a competitive margin between carbon, ballas and bort,
depending upon relative prices as
1 Mineral Industry, vol. 36 (1927), pp. 508-9.
2 Modem
usage has anglicized the old designation 'boart' into 'bort'. The use
of powdered bort in the polishing of diamonds was discussed as early as
1858 by a disÂtinguished contemporary French expert (Barbot, Traitc cotvplct des picrres prhieuses, Paris,
1858, p. 57): the price was then 15 gold francs per carat, or 12
shillings gold. In 1873, F. Boyle gave the price of carbonado as 185.
to 205. per carat, adding that 'it is . . . employed indiscriminately
with bort in the new boring machines' (To the Cape for Diamonds, London, 1873, p. 362).
