calcify
verb uk/ˈkæl.sɪ.faɪ/ us/ˈkæl.sə.faɪ/
[ I or T ]（尤指通过添加含钙物质）使变硬，硬化
to become hard or make something hard, especially by the addition of substances containing calcium
Foetal bones begin to calcify at about 13 weeks.
He has a form of arthritis that calcifies the spine.