striation vs virgule

striation

noun
  • One of a number of parallel grooves and ridges in a rock or rocky deposit, formed by repeated twinning or cleaving of crystals. 

  • The result of being marked with a stria. 

  • a parallel series of small grooves, channels, or impressions typically within a metal roof panel used to help reduce the potential for oil-canning. 

  • The action of marking with a stria. 

  • One of a number of parallel scratch lines in rock outcrops, formed when glaciers dragged rocks across the landscape. 

virgule

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