My periodic table poster is now available! Tourmaline (Dravite variant). I'm not sure why I have this mineral: I think it may have been a free sample included with some other mineral purchase. Lovely, though of relatively undistinguished chemical composition. Source: Theodore Gray Contributor: Theodore Gray Acquired: 20 September, 2005 Price: Donated Size: 1" Composition: NaMg3Al6(BO3)3[Si6O18](OH)3(OH)