Conversion of Diamond into Graphite
Although we cannot convert graphite inco diamond, we can change the diamond into graphite. A clear crystal of diamond is placed between two carbon poles, and the poles with intervening diamond are brought together and an arc formed between. The temperature of the diamond rapidly rises, and when it approaches 36000 C, the vaporising point of carbon, it breaks down, swells, and changes into black and valueless graphite.
Tribo-Luminescence
A few minerals give out light when rubbed. In the year 1663 the Hon. Robert Boyle read a paper before the Royal Society, in which he described several experiments made with a diamond which markedly showed tribo-luminescence. As specimens of tribo-luminescent bodies I may instance sphalerite (sulphide of zinc), and an artificial
