Calcify

[Sarah]

To make stony or calcareous by the deposit or secretion ofsalts of lime.

[Sarah]

To take something inherently temporary and tenuous and preserve it by making a separate, permanent rendering of it. The rendering may be either concrete or abstract.

[Tariq Zaki]

to become hard or make something hard, especially by the addition of substances containing calcium:

[Sarah]

Harden by deposition of or conversion into calcium carbonate or another insoluble calcium compound.