Figure 3.

BSE image and EDS analyses of PTS (sample Tv20ab). (a) Millimeter nodule embedded in the heart valve tissue. The nodule appears to be formed by a massive mineral formation with a low brightness in which smaller nodules with higher brightness are visible. The EDS spectra of these zones with different brightness are given in panels (b) and (c); these show that Ca, P, and O are the main chemical elements that made up the heart valve mineralized tissues, confirming their calcium phosphate nature. Mg, Na, and S were also detected; the massive mineral formation characterized by a lower brightness (spot a) than micrometric nodules (spot b) had a greater content of carbon (C) and sulphur (S) and represents a partially mineralized tissue while the micrometric nodules represent fully mineralized areas. The darkest zones represent the organic matrix not mineralized (lowest mean atomic number), while the black zones represent voids in the embedding material.