black as the ace of spades vs obsidian

black as the ace of spades

adj

  • Utterly black; pitch-black. 

obsidian

adj

  • black 

noun

  • A type of naturally occurring black glass produced by volcanoes. 

  • A slightly bluish black, the color of obsidian glass. 

How often have the words black as the ace of spades and obsidian occurred in a corpus of books? (source: Google Ngram Viewer )