The upper figure shows 3-D spatial models of various urban dust particles with multiple material phases in each particle. Darker-hued phases are more light-absorbing, lighter-hued phases are more light-scattering. Red material is strongly light-absorbing soot. The lower figure shows how the optical extinction efficiencies of various geometric-shaped particles compare with an actual Asian dust particle. In this case, the tetrahedron is closest to the actual particle.