nephrite vs verdigris

nephrite

noun
  • A semi-precious stone, one of the two types of stone commonly referred to as jade (the other being jadeite). 

verdigris

noun
  • A blue-green patina or rust that forms on copper-containing metals. 

  • The colour of this patina or material. 

verb
  • To cover, or coat, with verdigris. 

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