adobe vs ball clay

adobe

noun
  • An unburnt brick dried in the sun. 

  • The earth from which such bricks are made. 

  • A house made of adobe brick. 

ball clay

noun
  • A type of clay that commonly consists of 20-80% kaolinite, 10-25% mica, and 6-65% quartz. 

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