The Collaborative International Dictionary of English v.0.48:

Nitrocalcite \Ni`tro*cal"cite\, n. [Nitro- + calcite.] (Min.)
   Nitrate of calcium, a substance having a grayish white color,
   occuring in efflorescences on old walls, and in limestone
   caves, especially where there exists decaying animal matter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nitrocalcite
    n 1: the mineral form of calcium nitrate