gold mine vs opulence

gold mine

noun
  • A plentiful stockpile of something sought after. 

  • A mine for gold ore or metal. 

  • A very profitable economic venture. 

opulence

noun
  • abundance, bounty, profusion 

  • wealth 

  • ostentatious display of wealth and luxury; plushness. 

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