The Collaborative International Dictionary of English v.0.48:

Voltzite \Voltz"ite\, n. [So named in honor of Voltz, a French
   engineer.] (Min.)
   An oxysulphide of lead occurring in implanted spherical
   globules of a yellowish or brownish color; -- called also
   voltzine.
   [1913 Webster] Volubilate