Pyrolytical segmentation of natural algae and hydrothermal transformation of the calcium carbonate (CaCO3) skeleton of algae into FHA (Ca5(PO4)3OHxF1‐x). Particles consist of a pore system (mean diameter 10 μm), periodically separated (mean interval 30 μm) and interconnectedly microperforated (mean diameter of perforations 1 μm).