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Adamas, Diamond

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DIAMOND-CUTTING.                                 47
brilliant ono carat weight in Paris (1858) as 300 to 320 fcs.) The grand test with the jewellers of those 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. Some used the oil exuding from a roasted grain of wheat, others backed the stone with a bit of black silk. To set the Diamond transparent was never thought of before our times.
The White Topaz of Brazil is now the only stone which has any chance of being passed off for the Diamond. It is in truth extremely hard, and very brilliant, but wants the adamantine lustre and the iridescence.
It is a singular proof of the force of long-established fable to find the practical De Boot, though conjecturing, from its analogy to amber in the property of attraction, that the Diamond is " igneas et sulfurese natura?," yet goes on asserting that it is not only proof against fire, but even improved by exposure to its action for several days. Exactly a century later, Newton con­jectured it to be combustible, because its refractive power, which is to that of water as 1-0396 to '785, so greatly exceeds that due to its density.1 Soon after this Averani burnt a Diamond in the presence of Cosimo III. at Florence; but even then no one thought of performing the operation in the ordinary way : it must needs be effected by the solar rays concentrated with a burning-glass. At last some one trying the experiment in a smith's forge found the stone converted into charcoal at the melting point of silver
Adamas, Diamond Page of 453 Adamas, Diamond
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