*2.4. Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy*

The samples were observed without any pre-treatment with a FEI/Philips XL30 ESEM (low vacuum mode—1 torr, 20 kV, BSE detector). The possibility of working in "low vacuum mode" made it possible not to cover the samples with a conductive layer of carbon or gold. Depending on the size of the collected fragments, they were either observed whole or broken up to obtain a significant portion that was compatible with the size of the sample holder. The elemental analyses were carried out using an X-ray energy dispersive spectrometer, EDAX AMETEK Element, coupled to SEM.

A selection of fragments was also embedded in an epoxy resin, cross-cut with a diamond saw and then mechanically polished. Polished cross sections were then analyzed by SEM-EDX, too.
