Figure 3

Partial and final reconstructions of the Fe sample investigated at SENJU. (a–d) To reconstruct both small and big grains, extinction spots were divided in four size intervals and processed separately. Four 3D reconstructions are obtained by backprojection: (a) for spots with an area between 100 and 500 pixels, (b) for spots with an area between 100 and 1000 pixels, (c) for spots with an area between 100 and 2000 pixels, and (d) for spots with an area greater than 1000 pixels. In each reconstruction, different grains are shown in different colors. (e) The final reconstruction, obtained by combining the partial reconstructions, consists of 108 grains, each represented in a different color. The upper part of the sample includes a large powder-like region, probably due to oxidation effects occurred during the sample heating treatment. The powder-like region is reconstructed using an inverse Radon transform.