The Collaborative International Dictionary of English v.0.48:

Lithargyrum \Li*thar"gy*rum\ (l[i^]*th[aum]r"j[i^]*r[u^]m), n.
   [NL. See Litharge.] (Old Chem.)
   Crystallized litharge, obtained by fusion in the form of fine
   yellow scales.
   [1913 Webster]