Expose a fine diamond to the sunbeams, and carry it into a dark room,
when it will exhibit phosphorescence: and it has been stated that such
diamonds as do not display this peculiarity, may be made to do so by
dipping them into melted borax.
The diamond becomes phosphorescent also when fixed to the prime
conductor of an electrical machine, and a few sparks may be taken from
it. It likewise becomes electric by friction; and the Hon. Mr. Boyle
obtained electric gleams by rubbing two diamonds together in the dark.