Webster's Revised Unabridged Dictionary · 1913

Silicify

Silicify , transitive verb

[Latin silex, silicis, a flint + -fy: compare French silicifier.]

(Chemistry) To convert into, or to impregnate with, silica, or with the compounds of silicon.
The specimens found... are completely silicified. — Say

The silica may take the form of agate, chalcedony, flint, hornstone, or crystalline quartz.

Silicify , intransitive verb

To become converted into silica, or to be impregnated with silica.