melanoid vs obsidian

melanoid

adj

  • Relating to, or afflicted with, melanosis. 

  • Relating to, or resembling, melanin. 

noun

  • Synonym of melanoidin 

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 melanoid and obsidian occurred in a corpus of books? (source: Google Ngram Viewer )