is the imaginary part of the index of refraction, 𝑛 = 1 -𝛿 -𝑖𝛽 , with 𝑟 0 the classical electron radius, 𝑛 𝑎𝑡 the atomic number density, and 𝑓 2 the absorptive part of the X-ray scattering factor. The calculated linear attenuation coefficient using the stoichiometric 3:2 O:Fe ratio for hematite, does not reproduce the experimental data (blue solid line in Fig. ). This may arise from uncertainties of the atomic scattering factors at the L-edges. To reach an O:Fe ratio able to reproduce our data (solid red line in Fig. ), we need to increase the O:Fe ratio. To this purpose we introduce hexahydrate iron chloride (FeCl3•6H2O) (hexa) as a component of the linear combination with hematite (hema), 𝑐 • ℎ𝑒𝑚𝑎 +