42 NATURAL HISTORY OF PRECIOUS STONES, &c.
Some mineralogists have advanced the paradox that the Adamas of the Romans also
was not the Diamond, but the Sapphire. A sufficient answer to this is,
that such large Sapphires as the ancients frequently engraved (the
signet of Constantius, for instance weighing 53 carats) could not be
termed " punctum lapidis:" and besides this, the latter stone could not
have been engraved by means of its own fragments. The Sapphire, too,
usually occurs in masses of considerable relative size, especially the
grey sort, supposed, according to this theory, to represent the Adamas,
and these are mostly found rounded and pebble-shaped ; of a form, in
short, to be described by anything better than the term " punctum."
It
is, however, impossible to mistake Pliny's true meaning, especially if
a little attention be paid to his admirably chosen comparisons
exemplifying the characters of the gem. " The Indian appeared to have a
certain affinity to Crystal, being colourless and transparent, having
six angles, polished faces, and terminating like a pyramid in a sharp
point (laterum sexangulo laevore turbinatus in mucro-nem); or also
pointed at the' opposite extremities, as though two whipping-tops*
(turbines) were joined together by their broadest ends." A wonderfully
compact sumÂmary this of the distinctive features of the Diamond, for
the " six angles" can only belong to an octahedron, the
primary form of its crystallisation; the "two pyramids joined together
by their bases " expressing the case where the octahedron is perfect;
and the " natural polish " markÂing those small Diamonds, perfectly
crystallised, called " Naifes " by the Indians, completes the picture.
These Indian stones, the largest known to the Romans, attained
* The ancient shape of this toy was a many-sided pyramid, inverted.
