The Collaborative International Dictionary of English v.0.48:

Silicify \Si*lic"i*fy\, v. t. [imp. & p. p. Silicified; p. pr.
   & vb. n. Silicifying.] [L. silex, silicis, a flint + -fy:
   cf. F. silicifier.] (Chem.)
   To convert into, or to impregnate with, silica, or with the
   compounds of silicon.
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         The specimens found . . . are completely silicified.
                                                  --Say.
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   Note: The silica may take the form of agate, chalcedony,
         flint, hornstone, or crystalline quartz.
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