|Figure 2 of Harrit et al. (2009): Photomicrographs of red/gray chips from four different samples of the WTC dust. The inset in (d) shows the same chip edge on, revealing the gray layer. The 100 micrometer scale bars are 0.1 millimeters (mm) long.|
2Al + Fe2O3 --> Al2O3 + 2Fe (molten iron), ΔH = - 853.5 kJ/mole.
But if anyone feels the need for more smoking guns, they can be found here.