Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

nitrocalcite
     n : the mineral form of calcium nitrate