Source : Webster's Revised Unabridged Dictionary (1913)

Rensselaerite \Rens"se*laer*ite\ (r?ns"se-l?r-?t), n. (Min.)
   A soft, compact variety of talc,, being an altered pyroxene.
   It is often worked in a lathe into inkstands and other
   articles.

Source : WordNet®

rensselaerite
     n : a kind of soft talc; sometimes used as wood filler