The Romance of Modern Chemistry

 ELEMENTS WITH DOUBLE IDENTITY Fragments of diamond were obtained in this way, too small, however, to be of any value as gems. Although it is so difficult a matter to obtain even very small diamonds from charcoal or graphite, the reverse change can be quite simply effected. If a diamond is strongly heated it becomes more bulky and is converted into something that resembles coke or graphite; that is, it loses all the special crystalline character to which the diamond owes its brilliancy. The reader must bear in mind the distinction between artificial and imitation diamonds. Such artificial diamonds as were made by Moissan were the real article, and were found to consist of carbon. Imitation diamonds, on the other hand, contain no carbon; they consist of a soft, heavy flint-glass, known by the curious name of “ paste/’ One interesting way of distinguishing real from imitation diamonds is to bring them close to a little radium salt in a dark room; under this stimulus the real diamond phosphoresces, but the imitation article makes no re- sponse. The diamond is not only ornamental; it has many practical uses as well. One of the most remarkable things about it is its extraordinary hardness, in virtue of which it can scratch even a piece of hardened steel. With a fragment of a diamond fitted in a stem it is possible to write on glass as with a pen on paper, and with the natural edge of a small diamond crystal one can make a cut in a glass plate, so that the latter can be broken off like a piece of wood which has been nearly sawn through. The hardness of the diamond accounts also for its great usefulness in rock-boring tools; with a diamond drill, that is, a steel cylinder round the edge of which is fixed a series of diamonds, the hardest rocks can be gradually 55