FT-IR spectra of the experimental products. Spectra of quartz (Qtz), and amorphous silicate with SiO₂ composition (Am. SiO₂), enstatite composition (Am. En), and forsterite composition (Am. Fo) made by the ITP method are also shown for comparison. The maximum peak positions at around 10 µm were at 9.1 µm for Am.SiO₂ (blue dashed line), 9.7 µm for Am. En (green dashed line), and 10.1 µm for Am. Fo (orange dashed line), respectively.