Calcification is the accumulation of calcium salts in a body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue,[1][2] causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.[3] Calcification may also refer to the processes of normal mineral deposition in biological systems, such as the formation of stromatolites or mollusc shells (see Biomineralization).

Reference
Wiki: Arterial calcification