DIAMOND

(A corruption of flrfrtwzan^; from Gr.« priv., and ha/uMoi, I conquer, from its extreme hardne and difficulty of fracture.) The most valuable of the precioug stones. " Diamonds were originally discovered in Bengal, and in the Island of Borneo. About the year 1720 they were found in Brazil. They always occur in a detached state in alluvial soil. The primitive crystalline form of the diamond is a regular octahedron, of which there are numerous modifications. Diamonds are found of all colours: those which are colourle , or which have some very decided tint, are most esteemed; the latter, however, are rare. Tho5e which are slightly discoloured are the least valuable. The diamond is the hardest known substance, and can only be polished by its own dust or powder. The art of splitting or cutting and polishing this gem, though probably of remote antiquity in Asia, was first introduced into Europe in 148G by Louis Berghemof Briiges. who accidentally discovered that by rubbing two diamonds together their surfaces might be abradetl. They are cut chiefly into two forms, rose and brilliant: the latter have the finest effect, but require the sacrifice of a larger portion of the gem; so that the weight of an ordinary polished diamond often does not exceed half that of the rough gem. The largest known diamond is probably that mentioned by Tavernier, in po e ion of the great mogul: it was found in Golconda in 1550; is of the size of half a hen's egg, and said to weigh 900 carats. Among the crown jewels of Ru ia is a magnificent diamond, weighing 195 carats: it is of the size of a pigeon's egg, and was purloined from a brahmin i cal idol by a French scldier; it pa ed through several hands, and was ultimately purchased by the Empre Catherine for the sum of 90,000/. and an annuity of 4000/. Perhaps the most perfect and beautiful diamond hitherto found is a brilliant brought from India by a gentleman of the name of Pitt, who sold it to the regent Duke of Orleans for the sum of 100,000/. It weighs about 136 carats, or 544 grains. That the diamond is combustible, was first proved by the Florentine academicians m 1694, who found that when exposed to the heat of the sun concentrated in the focus of a large lens, it burned away with a blue lambent flame. The products of its combustion were first examined by Lavoisier in 1772, who showed that when it was burned in air or oxygen it produced carbonic acid: sub. sequent experiments have shown that nothing but carbonic acid is thus formed; and hence it is proved that the diamond is charcoal or carbon in a pure and crystalline form. DIANA. [s. 349]