The Collaborative International Dictionary of English v.0.48:

Schorl \Schorl\ (sh[^o]rl), n. [G. sch["o]rl; cf. Sw. sk["o]rl.]
   (Min.)
   Black tourmaline. [Written also shorl.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

schorl
    n 1: black tourmaline