Schorl, and the Pyroelectric Stone

Black tourmaline, the variety called schorl, is the iron-rich end of the tourmaline group, a complex boron silicate that forms long striated prisms. Tourmaline is notably pyroelectric and piezoelectric: heated or compressed, a crystal develops opposite electric charges at its two ends, a property Dutch traders in the eighteenth century knew as its habit of attracting and then repelling ash, and which gave it the early name aschentrekker, ash-drawer. That real physical effect is the factual kernel beneath the modern reputation of the stone. In the crystal-healing literature of the late twentieth century onward, black tourmaline is the standard protection and grounding stone and is widely sold for shielding against electromagnetic fields; there is no scientific support for the shielding claim, and the association is a New Age development rather than a traditional attribution.

Schorl, the name for the iron-rich black tourmaline recorded here, is inherited unchanged from Schorl, a village (now Zschorlau) in the Saxon Erzgebirge where tin miners had long found the mineral among their ore; German mineralogists were using the local place name for the stone by the sixteenth century, well before tourmaline as a family was distinguished from other dark crystals. The pyroelectric effect noted above was studied scientifically in the eighteenth century by Franz Aepinus, who in 1756 gave the first physical description of how a heated tourmaline crystal develops opposite charges at its two ends, turning a curiosity of Dutch traders into an object of early electrical science.