Diamond

(dī'mund.) [A corruption of adamant, from adam as-a, not, and dam as, I subdue-on account of its hardne .) (Min.) Pure carbon in a transparent crystalline form, and the hardest substance known. Sp. gr. 3-5 to 3.6. It is generally colorle , but sometimes tinged red, orange, yellow, green, or blue. The index of refraction is 2439, being exceeded only by chromate of lead and orpiment. It is unaffected by any liquid, and infusible at the highest attainable temperature. Before the oxy-hydrogen blowpipe it gradually burns away, and the same takes place when it is heated white-hot and plunged into an atmosphere of oxygen, carbonic acid being produced. Exposed to the intense heat of the voltaic arc, the D. becomes converted into graphite. Besides its value as a gem, it is of great use in the arts and manufactures. D. dust is used for cutting and polishing other gems; the edge of a native crystal is used by glaziers for cutting gla ; a sharp point is used for scratching and engraving on 2 1 4 5 6 3 Fig. 262.- DIAMONDS. 1, 2. Brilliants when cut (vertical and lateral appearance); 3, Brilliant before being cut; 4, 5, Rose-cut diamonds; 6, Table cut diamond. gla ; a splinter is also used as a tool for turning gla lenses in a lathe; and rough D., too imperfect to be used as gems, are mounted as boring-tools for perforating rocks. -Rose D., one which is quite flat underneath, with its upper part cut in numerous little faces, usually triangles, the uppermost of which terminate in a point.- Table D., one which has a large square face at top, encompa ed with four smaller.-Brilliant D., one which is cut in faces both at top and bottom, and whose table or principal face is flat. In cutting diamonds the first step is to cement them at the ends of two pieces of wood, which are held in the hands and rubbed together (Fig. 262). Diamonds are found in Borneo, Golconda, Bengal, Brazil, and of late years on the banks of the rivers in Cape Colony.-(Geom.) The Lozenge, q. v.-(Print.) See TYPE. [s. 283]