Minerals acquire electricity through friction or heating, and in this
state readily attract or repel small bits of paper and other light
substances.
All minerals are electric, some displaying positive and others negative
electricity.
The electric test of a precious stone refers to the length of time that
a stone will retain electricity after friction or heating.
Some stones lose this quality in a few minutes, while others retain it
a long time. The tourmaline is noted for its electrical properties,
while the Brazilian topaz rendered electric by heating or rubbing has
been known to affect the electric needle after 32 hours.