DIAMOND

(A corruption of adamant; from Gr. o, priv., and 6 t/iato, J conquer, from its extreme hardne and difficulty of fracture.) The most valuable of the precious stones. Diamonds were originally discovered in Bengal, ainl in the bland of Borneo. About the year 1720 they (baud in Brazil. They always occur in a detached state in alluvial soil. The pnmilive crystalline form of the di.linoud is a regular octahedron, of which there are numerous modifications. Diamonds are found of all colours: those which are colourle , or whicli have some very decided tint, are most esteemed; the latter, however, are rare. Those which are slightly discoloured are the least vahiable. The diamond is the hardest known substance, and can only be polished by its own dust or powder. ot of splitting or cutting and polishing this gem, though probably of remote antiquity in Asia, was first introduced in to Europe in I486 by Louis It•■rgln-m of Bruges, who accidentally discovered that by rubbing two diamonds together their surfaces might be abraded. They are cut chiefly into two forms, ruse 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 Tavernler, in poweation of the great mogul: it was found in Oolconda in 1560; is of the size of half a hen's egg, and • w.igh 900 carats. Among the crown jewels of da is a magnificent diamond, weighing 195 carats: it is if a pigeon's egg, and was purloined from a brahuiiniial idol by a French soldier; it pa ed through several hand*, and was ultimately purchased by the Empre CaUterine for the sum of 90,00W. 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 100,0007. It weighs about 136 carats, or 514 grains. That the diamond is combustible, was first proved by the Florentine academicians in IC94, 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 Lavoisierin1772, who showed that when it was burned in air or oxygen it produced carbonic acid: subsequent experiments liave 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. [s. 353]