An expert in gems has lately called attention to a property in the diamond which has not hitherto been fully appreciated. Robert Boyle mentions a diamond that became phosphorescent simply by the heat of the hand, absorbed light on being held near a candle, and emitted light on being briskly rubbed. Observations by Mr. Kunz, the gem expert, confirm Boyle’s statement that diamonds become phosphorescent in the dark after exposure to sunlight or electric light by being rubbed on wood, cloth, or metal. This property is an important one, as it will help the non-expert to distinguish between the true diamond and other hard stones, as well as imitations, none of which is said to exhibit this phenomenon.
One of the most famous phosphorescent diamonds is the Hope Diamond, which phosphors red.
