1 14 NATURAL HISTORY OF PRECIOUS STONES, &c.
by Emanuel at ten per cent, each year, so that he puts down the selling price for the year 1865 at 18l.
This only applies to small stones ; specimens of unusual size, from the
difficulty of finding purchasers, necessarily have their value
calculated by other rules. In the suit ' Van Minden v. Pyke,'
referred to above, it was stated in the evidence, that Diamonds had
risen 25 per cent, in value since the year 1861, and large stones in
even a greater proportion. This rise may be attributed to many causes,
the diminution in the value of gold, the extinction of the supply of
Indian Diamonds, and the constantly decreasing productiveness of the
Brazilian mines ; whilst on the other hand the demand for them daily
augments through the craving after this outward and visible sign of
opulence in the mushroom growth of ' nouveaux riches ' that has sprung
up within the above-named space of time, both here and, with e,ven more
marvellous rapidity of vegetation, in the salons of Paris.
The
grand test with the jewellers of olden times for distinguishing the
real Diamond from the spurious, of which so many were then current, as
the White Sapphire, the Citrine Beryl, and the Crystal cut into' a
pyramid, was to ascertain whether it would " take the tincture." This
was a varnish made of ivory black and mastich applied to the back of
the stone, which, if a true Diamond, obtained vast brilliancy from this
background ; but if any other gem, became dull and lustreless, shewing
the black through its substance. Some used the oil exuding from a
roasled grain of wheat darkened with ivory black, others backed the
stone with a bit of black silk. An ingenious, and often too deceptive
mode, of evading this test was to set the imitative Diamond with a
vacancy between its " culasse " and a black back-ground, the air
confined in this space preventing the rays of light from being stopped
too suddenly by the
