ammonia alum vs tschermigite

ammonia alum

tschermigite

noun

  • a water-soluble mineral, ammonium aluminium sulphate (NH₄)Al(SO₄)₂·12(H₂O) found in fumaroles and similar environments 

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