The Collaborative International Dictionary of English v.0.48:

Strontia \Stron"ti*a\, n. [NL. strontia, fr. Strontian, in
   Argyleshire, Scotland, where strontianite was first found.]
   (Chem.)
   An earth of a white color resembling lime in appearance, and
   baryta in many of its properties. It is an oxide of the metal
   strontium.
   [1913 Webster]