igneous vs pyrogenous

igneous

adj
  • Pertaining to or having the nature of fire; containing fire; resembling fire. 

  • Resulting from, or produced by, great heat. With rocks, it could also mean formed from lava or magma. 

pyrogenous

adj
  • Synonym of pyrogenic 

  • Synonym of pyrogenetic 

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