Conversion factors for mass- or volume-normalized absorption coefficients of particles relative to bulk material in the small-absorption limit (k ≪ n). Curves for variable material refractive index are given for the cases of small PE-embedded (refractive index n_m = 1.52) and non-embedded (matrix vacuum) spherical and ellipsoidal (CDE model, Bohren & Huffman 1983) particles. The curves are labeled with the symbols used in the text. The vertical dotted line indicates an average value of the refractive index for forsterite and enstatite in the submillimeter spectral range (n = 2.66).