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54
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The Diamond.
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Rundle
& Bridge, for a sum which gave him a large profit. Long before
Wollaston's time, however, there must have been many students of
Precious Stones who were familiar with the cleavage of the Diamond.
Thus De Boot, writing in 1609, tells us that he knew a physician who
boasted that he could " divide a Diamond into small scales like a piece
of talc." The fracture of the Diamond, apart from its cleavage, is
conchoidal, and here and there the stone is liable to split off in
fragments.
Among
the physical properties of the Diamond that of hardness is pre-eminent
; a quality in which it so exceeds all other bodies that it can
penetrate them without being itself even scratched. In consequence of
its excessive hardness it was formerly only possible to polish it
partially, by rubbing it against another rough Diamond—a process which
is known as " bruting." In early times there existed so exaggerated an
idea of its extraordinary hardness that it was said a Diamond could
not be broken by a hammer on an anvil, and that it was far easier to
strike the anvil into the earth than to break the Diamond. This will
account for the loss of many Diamonds in antiquity, as it was the
absurd practice to place them upon the anvil to test their genuineness.
Through this ignorance many a regal gem has been shattered and so lost
to the world. It was, of course, only the brittleness of the stone which was really tested by the hammer, and not its hardness, which is a very different quality.
Pliny
gives a detailed account of the Diamond in his " Natural History,"
xxxvii., 15. As translated by old Dr. Holland, he says : " The most
valuable thing on earth is the Diamond, known only to kings, and to
them imperfectly. ... It is only engendered in the finest gold.....Six
different kinds are known. Among
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