posure to great heat,* first split, then emitted bright red
sparks, and at last was consumed, leaving nothing except carbonic acid gas and a very small quantity of ash. Boyle had
previously found that it was combustible, but the correct explanation of the phenomenon belongs to Lavoisier, a French chemist
(1743-1794), who not only burned the diamond, but also discovered the true nature of its constituent. Several other
experiments were subsequently made establishing the fact of
its combustibility, one at Vienna in 1750, and another at Paris in
1771, so that no reasonable doubt in regard to it remains ; still, it
was thought the diamond might resist the influence of great heat
under certain conditions, and an experiment was made in which
air was entirely excluded ; the stone was neither consumed nor
melted, the latter fact proving it to be infusible.\
Some experimenters have thought they detected a cellular
structure in the residuum, indicating the vegetable origin of this
precious stone ; but this fact is not, in the opinion of others,
well substantiated.
Color.—A large part of the diamonds are white, though a
perfectly transparent, colorless gem is more rare than is generally supposed ; the remainder present a diversity of hues of
different shades, including yellow, red, blue, green, brown,
and black. The action of heat in modifying or changing
the color has been proved by repeated experiments ; in some
cases, the original tints are restored after a certain time,
but in others the acquired hues are permanent. Though
* It is said that 140 Wedgewood, or five thousand Fahrenheit, is necessary to
burn the diamond.
t After the great conflagration at Hamburg in 1842, a large number of diamonds, which had only been defaced by exposure to the heat, were sold for a trifle,
under the mistaken idea that they had been permanently injured, but after being
repolished they regained their former brilliancy and lustre, with no other loss
than a slight reduction in weight.
