Tourmaline
Name
Reported by Christianus-Fridericus Garmann in 1707. The name "tourmali" was a generic name used in Ceylon [Sri Lanka] for coloured gems, mostly zircons. About 1703, it had been discovered by Dutch lapidaries that some of the "zircons" arriving in the Netherlands were actually a previously undescribed mineral. Several names were given to the new mineral including "Pierre de Ceylan, by Lemery in 1717. Tourmalin, as a more or less specific mineral name, was used by Rinmann in 1766. Hill called it Tourmaline Garnet in 1771 and Richard Kirwan shortened the name to "Tourmaline" in 1794.Physical Properties
Hardness: 7 on Mohs scaleFracture: Irregular/Uneven, Conchoidal
Density: 2.9 - 3.1 g/cm3 (Measured)
Chemical Properties
Formula: A(D3)G6(T6O18)(BO3)3X3ZA = Ca, Na, K, or is vacant (large cations);
D = Al, Fe2+, Fe3+, Li, Mg2+, Mn2+ (intermediate to small cations - in valence balancing combinations when the A site is vacant);
G = Al, Cr3+, Fe3+, V3+ (small cations);
T = Si (and sometimes minor Al, B3+);
X = O and/or OH; and
Z = F, O and/or OH.