strip mine vs treasure trove

strip mine

noun
  • A mine where the material above the ore is removed (stripped) to expose it for removal and use. 

treasure trove

noun
  • Precious metal objects that were buried or concealed by an unknown owner. 

  • A valuable discovery. 

  • A hidden treasure, subsequently discovered. 

  • A place where many things of value can be found. 

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