Characterisation of the clathrite samples. (A) Images of the three synthesised clathrites. (B) Near-IR spectra of Ca-clathrite (black line), Mg-clathrite (red line), and Na-clathrite (blue line). (C) Characteristic Raman peaks of MgOH used in the Mg-clathrite synthesis experiment (left). Raman spectra of Mg-clathrite in formation at three different times. The disappearance of the peak around 280 cm⁻¹ indicates the depletion of the initial MgOH (right).