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Some precious stones display a distinct phosphorescence after exposure to the sunlight, and also upon the application of artificial heat, and through mechanical and electrical means.
Many diamonds, when taken to a dark room, appear quite luminous; this is also true of topaz, fluor spar, and other minerals.
ELECTRICITY.
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. |
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Precious Stones Guide Vol 1
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