Photomicrographs and SEM images of putative microbial structures, euendolith borings, and pyrite framboids. (a) SEM image of microscopic spherical cavities (~0.5 – 1 μm in diameter) within PCG cortex. Sample BBR0. (b) Close-up of image A. Sample BBR0. (c) SEM image of sample dissolved in acetic acid, which reveals phosphatized euendolith borings (dashed line). Sample NPP 17.5. (d) Photomicrograph in plane-polarized light of filamentous structures (black arrows) within phosphate and microscopical spherical cavities with distinct rim (red arrows) resembling microbial remains. Sample PC 7. (e) SEM image of sample dissolved in acetic acid, which reveals an aggregation of pyrite framboids. Sample NPP 17.5. (f) Backscatter SEM image of pyrite framboids within phosphate. Sample PC 7.