Source : Webster's Revised Unabridged Dictionary (1913)

Zinnwaldite \Zinn"wald*ite\, n. [So called after Zinnwald, in
   Bohemia, where it occurs.] (Min.)
   A kind of mica containing lithium, often associated with tin
   ore.

Source : WordNet®

zinnwaldite
     n : a mica containing iron and lithium