62 NATURAL HISTORY OF PRECIOUS STONES, &c.
discovered
a menstruum distilled from antimony ("aqua mercurialis ex stibio
distillata") by means of which, with the application of heat, he was
enabled to clear diamonds of the flaws, clouds, and colours which
detract so greatly from their value. De Boot declares that he had seen
a stone bought for 6000 ducats in the first instance, which after
having been thus " emendated " was valued at double that amount. "
But," adds he, " a secret like this must be divulged to none." It
therefore, like numerous other important arcana of those tentative
philosophers, has perished with the discoverer. And now in our day
comes forward Barbot, who doubtless has never heard of Rudolf II., and
boasts of having attained to the same desideratum, styling himself on
his title-page " Inventeur du procédé de décoloration du Diamant brut."
But yet he has not advanced so far as the Imperial adept, for his
invention merely consists in removing by some chemical means (a secret)
the dull crust of the native crystal, thus enabling its exact nature to
be ascertained before cutting, so that the purchase of the stone will
no longer be a complete lottery as to its result. In the very curious
case 'Van Minden υ. Pyke' tried at Croydon, August 9, 1865, to the utter bewilderment of both judge, counsel, and jury, and which turned upon the identity of
a particular large Diamond, alleged to have been changed by the person
entrusted with its sale, it was stated in the evidence that it is a
common practice when a large stone is disfigured by a yellow flaw,
to roast the same in a crucible filled with borax ; the operation
changing the yellow into a bluish-black, becoming rather an improvement
than otherwise to the lustre of the stone, if successfully performed.*
But in this instance, from want of skill in the management of the fire,
the
* Mawe gives full directions for the process (p. 33).
