Ultrastructure and x-ray microanalytical study of human pineal concretions.

We examined human pineal concretions and found them to exhibit a multi-layered concentric structure consisting of irregularly spaced dense and sparse zones containing fine crystals. The hydroxyapatite crystallites were shown to be irregularly outlined plate forms (measuring 11-70 nm in their longest dimension and 2-10 nm in thickness). At the center of each crystallite a central dark line was observed by means of high resolution electron microscopy. The structure and size of the crystals were similar to those of dentin and bone. The ground surface of the concretions was observed metallurgically by means of an electron probe microanalyzer (EPMA). The surface zones of the concretions contained a higher concentration of zinc, which seems to play an important role during the mineralization process, whereas calcium and phosphorus exhibited higher concentrations at the center.