The Collaborative International Dictionary of English v.0.48:

Indurate \In"du*rate\, v. t. [imp. & p. p. Indurated; p. pr. &
   vb. n. Indurating.]
   [1913 Webster]
   1. To make hard; as, extreme heat indurates clay; some
      fossils are indurated by exposure to the air.
      [1913 Webster]

   2. To make unfeeling; to deprive of sensibility; to render
      obdurate.
      [1913 Webster]