﻿U. 
  S. 
  GEOLOGICAL 
  SURVEY 
  

  

  BULLETIN 
  NO. 
  322 
  PL. 
  V 
  

  

  DIATOMACEOUS 
  SHALE. 
  

  

  A. 
  Typical 
  soft, 
  white, 
  unaltered 
  specimen. 
  B. 
  Red, 
  brittle, 
  and 
  heavy 
  specimen: 
  metamorphosed 
  

   3V 
  by 
  the 
  burning 
  of 
  its 
  hydrocarbons. 
  

  

  