(1 -𝑐) • ℎ𝑒𝑥𝑎, and fit the experimental data leaving the hematite proportion as free parameter. The best fit was obtained with only 42% hematite and 58% FeCl3•6H2O. It is interesting to note that the extracted thickness after the fitting procedure is closer to the expected value, due to the lower density of FeCl3•6H2O (1.82 g/cm 3 ) compared to hematite (5.3 g/cm 3 ). Considering the synthesis of our samples, which used FeCl3 in aqueous solution, we choose FeCl3•6H2O to introduce a higher O:Fe ratio. We proceed in a similar way using a sample obtained by drop casting 1µL of FeCl3 from an aqueous solution with pH =1. The result is presented in regions marked with a, b, and c respectively, to extract the relative hematite composition applying the approach described above. As an example, Fig. shows the spectrum from region c. The hematite content corresponds to 21% hematite in the 135 nm thick nanorod. Regions a and b were found to have 25 and 31% hematite, with 117 and 135 nm thickness, respectively. Aside from the hematite content being very low, possibly somehow underestimated within this approach, it is clear that the nanorod is chemically heterogeneous. There are indeed contrast variations in the STXM image shown in Fig. inset, but this direct imaging approach fails in extracting more valuable information. It is worth mentioning here, without further details, that we didn't succeed in getting more information using the PCA (Principal Component Analysis) -cluster analysis as implemented in MANTIS (Multivariate ANalysis Tool for Spectromicroscopy) software . Indeed, we observe the same compositional variations along the nanorod, without evidence of spatial distribution or spectral identification.