*3.4. Metallic Aluminum Al<sup>0</sup>*

The content of Al0 in FA is shown as a boxplot in Figure 4 (a complete table can be found in the Supplementary Materials). Two samples (FA01, FA04) show content above 1.4 wt.%, five samples (FA02, FA06, FA10, FA14, FA26) contain 0.8–1 wt.%, and most of the samples are between 0.1 and 0.6 wt.%. Two samples contain no Al0. Overall, the Al0 content is on average 30% of the total aluminum in FA.
