Figure 8

a FTIR of OH-signified calcite (C), aragonite (A), and magnetite (M) of the same specimens as in Fig. 1, showing the OH⁻ stretch at 3,400 cm⁻¹ and characteristic absorption bands of the three phases as labeled and assigned in text. The corresponding Raman spectrum b shows the characteristic peaks with assigned vibration modes in text. There is considerable frequency change due to defects and partial disorder (cf. text)