What's the difference between petrification and silicification?

Petrification

Definition:

Example Sentences:

(1) Cholesterosis of the gallbladder ist a reversible process, the petrification of cholesterol polyps is repeated observed.
(2) 12 of 16 patients demonstrated changes which were characteristic for hypocorticism: in 4 patients (no signs of tuberculous involvement of the adrenals) a decrease in their sizes with the preserved regular shape was noted, in 8 patients (with clinicolaboratory findings of tuberculous involvement) enlarged sizes, bilateral deformity of the contours and the presence of petrificates were detected.
(3) Changes in the brain matter were detected in 13 of these 15 patients: foreign bodies (2 cases), meningeal cerebral cicatrices (5), dilatation of the ventricular system (4), petrificates in the brain matter (1), atrophic changes of the cerebral cortex (1).
(4) The formerly feared "linear scar petrification," usual after use of Teflon felt, was absent.

Definition:

(n.) Thae act or process of combining or impregnating with silicon or silica; the state of being so combined or impregnated; as, the silicification of wood.

Example Sentences:

(1) A model is put forward that provides for a conceptual framework for continued studies in this area, and provides testable hypotheses which should lead to a greater understanding of biomineralization processes in general and silicification in particular.
(2) Preliminary freeze-substitution studies have located silicon, as well as potassium and chloride, in the cell vacuole and wall deposition sites during initial silicification.
(3) Botanical investigations have focused on silicification of cell walls in relation to plant development, using scanning and transmission electron microscopy combined with X-ray microanalysis.