opalescent vs prismatic

opalescent

adj
  • Exhibiting a milky iridescence like that of an opal. 

prismatic

adj
  • Of or pertaining to a prism; having the form of a prism; containing one or more prisms. 

  • Separated or distributed by, or as if by, a transparent prism; formed by a prism; varied or brilliant in color. 

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