Amorphous calcium precipitations in human aortic valve.

Spheroidal, granular, and fibrillar particles were observed in human aortic valve calcifications. Spheroids were similar to amorphous calcium phosphate shown previously in syn thetic preparations and in bone. The frequent coexistence of needle shaped hydroxyapatite crystals with granular and fibrillar particles suggests that the latter are also amorphous calcium phosphate and may be precursors of hydroxyapatite. All three types of particles had a tendency to form laminated and spherular secondary and failed to give a crystalline pattern by electron diffraction.