“…SEM imaging of materials occupying the centers of calcification showed that these are morphologically distinct from the surrounding fibers. The materials at the centers of calcification have been variously described as small, nano-crystals, very fine, or granular (e.g., Wainwright, 1964;Constantz, 1986;Clode and Marshall, 2003). Selective analyses of centers of calcification and adjacent fibers indicate that centers of calcification are also compositionally distinct.…”