- A complex black or dark-coloured borosilicate mineral, compounded with various chemical elements and considered a semi-precious stone.
2012 March 1, Lee A. Groat, “Gemstones”, in American Scientist, volume 100, number 2, page 128:
- Although there are dozens of different types of gems, among the best known and most important are […] . (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)
- A transparent gemstone cut from it.
tourmaline f (plural tourmalines)