1) Black tourmaline 2) Tourmaline 
tourmaline
• (n.) Black tourmaline.
(from the article `greisen`) Greisen is closely connected with schorl, both in its mineralogical composition and in its mode of origin. Schorl is a pneumatolytic product ...
Schorl (shôrl) noun [ German schörl ; confer Swedish skörl .] (Min.) Black tourmaline. [ Written also shorl .]
Schorl is a rock comprised of quartz and black tourmaline (schorl). It is of igneous origin and occurs associated with granite and crystalline schists. It has a granular texture and is usually a grey colour. It is a frequent associate of tin-bearing veins in all parts of the world.
noun black tourmaline
(complex Sodium Iron Boro-Aluminum Silicate) Schorl is the most common mineral in the Tourmaline Group . Some other members of the Tourmaline Group are elbaite , uvite , buergerite and dravite . All tourmalines form similar crystals because they are isostructural, meaning that they share the same internal crystalline stru...