Triboluminescence and Piezoluminescence 383 



the fact that two pieces of quartz or of flint rubbed against each 

 other would emit light and give off a smell of sulphur. He also 

 found that emerald, hyacinth, amethyst, topaz, and carneol would 

 luminesce when rubbed in a hot oven. These experiments were 

 confirmed by J. H. Pott, who observed flint, quartz crystals, and 

 porcelain triboluminescence in 1757, while Robert de Paul de 

 Lamanon (1752-1787), the French naturalist, in 1785 again men- 

 tioned the sparks which appeared on striking flint and other 

 minerals. He suggested that the sparks indicated an actual burning 

 of the material, since diamonds will burn. Although such sparks 

 from flint cannot come from burning (oxidation) as do sparks from 

 iron, they undoubtedly represent incandescent particles and must 

 not be confused with the triboluminescent phenomena of quartz or 

 flint. G. G. Schmidt (1795) noted " phosphorescence " of quartz 

 when rubbed with precious stones. 



Many other natural minerals are triboluminescent. Of special 

 interest are zinc ores, because of the present importance of various 

 zinc sulphide phosphors. The physician, Samuel Theodor Quell- 

 malz (1696-1758) , at various times a professor of anatomy, surgery, 

 physiology, pathology, and therapy at the University of Leipzig, 

 observed in 1735 that calamine (a native hydrous zinc silicate) and 

 also " Cadmia fornacum," the zinc oxide encrustaced on furnaces, 

 luminesced on touching or handling. A little later, in 1744, the 

 councillor of mines, Johann Friedrich Henckel (1679-1744) , ob- 

 served luminescence on scraping these compounds with a knife, as 

 did Johann Gottlob Lehmann, (died 1767) , a physician in Berlin 

 who became professor of chemistry and director of the Royal Mu- 

 seum of St. Petersburg, in 1749. 



A Dr. C. G. Hofmann, writing for the Hamburgische Magazin in 

 1750, reported that zinc blend (ZnS) from Scharfenberg ^ would 

 become strongly luminescent on rubbing and endeavored, without 

 success, to remove the property by treatment with various chemicals. 



Tobern Olof Bergmann (1735-1784) also, the great Swedish 

 chemist and naturalist, knew of these phenomena. In 1772, Joseph 

 Marie Francois Lassone (1717-1788), French physician to royalty 

 and a student of chemistry, saw the luminescence of zinc oxide, 

 obtained by burning zinc, shaken in a flask. ^V^hen stirred, the light 

 was said to last for an hour. 



Thomas Wedgwood's (1792) experiments on triboluminescence 

 were made by what he called attrition, by striking or rubbing two 

 pieces of the material together. Rock crystal (quartz) was the 

 brightest, then diamond, both giving a whitish light, then white 



* See also Sven Rinman (1747) on thermoluminescence of fluorspar. 



