jewel vs mother lode

jewel

noun
  • Anything precious or valuable. 

  • A precious or semi-precious stone; gem, gemstone. 

  • A valuable object used for personal ornamentation, especially one made of precious metals and stones; a piece of jewellery. 

  • A bearing for a pivot in a watch, formed of a crystal or precious stone. 

  • Any of various lycaenid butterflies of the genus Hypochrysops. 

  • The clitoris. 

verb
  • To bejewel; to decorate or bedeck with jewels or gems. 

mother lode

noun
  • Any source of valuable or useful material. 

  • A large or rich vein of gold or of another precious mineral from which other branches extend. 

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