Many different samples of WTC dust have been examined visually and microscopically and reported on here. Other published articles have reported very similar microscopic data, including all of the heterogeneous features mentioned in the Results section. These results are compared to images of the large scale damage to the WTC and the resulting aftermath. This paper concludes for the first time that the World Trade Center was turned into at least two different types of dusty metallic foam. Several types of foam contain a previously unreported high level of iron, in the form of iron chips and microspheres. All types of dust/foam contain each of a number of features, but in different proportions. The different proportions indicate that the different types of dust came from different sections of the WTC buildings. The darker foam came from the elevator shafts and steel columns, and the medium gray foam came from the main part of the buildings that contained the majority of the concrete, ceramics and gypsum wallboard and contains many dark, metallic chips and fragments, but a higher proportion of white and mixed colored crystals. The very lightest colored dust, which contains the highest proportion of fibers likely came from the exterior of the building where the windows were located.
A unique specimen was discovered among other samples of WTC dust. This piece of dust contained two very differently colored types of dust attached to each other, medium gray and dark gray with rusty colored spots. It was visually obvious that each type of dust contained tiny air pockets, but the dark gray dust seemed more uniform (except for the rusty looking spots), while the medium gray dust seemed to have more different types and colors of particles. Samples were taken of the medium gray dust, the dark gray dust and the rusty colored spots, labeled A-C respectively.
An abundant amount of white crystals of varying size are seen in the medium gray dust samples seen in Figure 5A, but relatively few black chips, red chips, fibers, shiny silver droplets and possible white and black microspheres are noted. The dark gray dust (Fig. 5B) contained a higher proportion of dark gray chips along with red chips, white crystals, shiny silver droplets and, some fibers and black and white microspheres are noted. Samples from the rusty red spots were isolated and examined microscopically (Fig. 5C). Not surprisingly, these samples contain a higher proportion of red colored chips and dark gray chips, but white crystals, silvery droplets and even a few fibers are noted. Some samples include large white spheres of material.
The lightest gray dust was sampled and examined microscopically in (Fig. 6A). The greatest abundance of fibers was noted in this sample, along with white crystals, dark gray chips, red chips and white microspheres. What is unique about this sample compared to the other samples examined in this paper is that it was collected from several blocks away from the WTC complex. Several chips were discovered that had red and gray layers (Fig. 6B). Other reports exist of such layered chips, and the presence of these chips leads further credibility to the idea that the samples reported on in this paper are representative of the WTC dust examined in other published work on the subject.