DIAMOND

a mineral which consists of pure crystallized carbon, and, unlike most minerals, is found in single crystals. As a rule they are of octahedron form, but have also been found in rhombic dodecahedra and hexakis-octahedra. The color of diamonds varies, the rarest being clear like gla , and sometimes this variety is tinted with delicate hues of yellow, grey, blue, green, or red. Black diamonds are not own. In their virgin state the stones have a rough, dull, and uneven surface, and, in fact, workers in Brazilian gold mines regarded them as nothing more than worthle pebbles until the 18th cent., when their true value was accidentally discovered. The diamond is so hard that it is impo ible to scratch it except with another diamond. Impure crystals and fragments, which are of no use for decorative purposes, are called bort, and in 1476 L. von Berguen of Bruges found that this might be used for engraving and polishing perfect stones. Bort is used also for polishing and faceting other precious stones, whilst small diamonds are used for cutting gla , drilling porcelain, and as bearings for watches. Diamond cutting, a highly specialized art, is carried on chiefly at Amsterdam and Antwerp. Some famous diamonds are the Koh-i-no or, presented to Queen Victoria by E. India Co.; the Regent or Pit, one of the Fr. crown jewels; the Star of the South, found in Brazil; the Cull in an, largest diamond of good quality yet discovered; and the Blue Hope diamond, supposed to bring ill-luck. Experiments have been made (notably by Sir William Crookes, Mr. MacTear, and M. Moi an) to manufacture artificial diamonds in crucibles, and very small stones have been produced.