Extinction, absorption, and scattering opacity of bare grains (dashed) and ice coated grains (solid). A constant thickness of ice layers is assumed for all grains (q = 0). The composition of grains is Mg_0.7Fe_0.3SiO₃, amorphous carbon, and porosity in the ratio 0.60:0.15:0.25, and that of ices: H₂O, CH₄, NH₃ in the ratio 0.60:0.20:0.20. The volume of dust is V_BG = 6.2894 × 10⁻¹³ cm³ cm⁻³ and thickness of ice is Δa = 0.246 µm. Refractory dust grain size distribution parameters are a_min = 0.05 µm, a_max = 3 mm, and powerlaw index 3.5. These opacities have been calculated using effective medium theory.