calcification -
The process of change into a stony or calcareous substance by the deposition of lime salt; -- normally, as in the formation of bone and of teeth; abnormally, as in calcareous degeneration of tissue.
Wikipedia
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.