speleothem vs stalagmite

speleothem

noun
  • Any secondary mineral, deposited in a natural cave by the action of water. 

stalagmite

noun
  • A secondary mineral deposit of calcium carbonate or other mineral, in shapes similar to icicles, that lies on the ground of a cave. 

  • Coordinate term: stalactite 

How often have the words speleothem and stalagmite occurred in a corpus of books? (source: Google Ngram Viewer )