Black Tourmaline Point PolishedA polished point cut from one of the most electrically active minerals knownTourmaline generates a measurable charge when compressed or heated. Black Tourmaline (Schorl) is a boron silicate, Mohs 77. 5, and a genuinely piezoelectric and pyroelectric mineral: it generates an electric charge under mechanical pressure and temperature change, a property applied in pressure gauges and other scientific instruments. Its black color reflects high iron