Extinction of olivine and pyroxene in the mid- and far-infrared

The extinction coefficients Q_ext/α of orthopyroxene, clinopyroxene, $${\text {Fo}}_{100}, {\text {Fo}}_{90}, {\text {Fo}}_{80}, {\text {Fo}}_{60}, {\text {Fo}}_{40},$$ and the Allende meteorite have been obtained in the mid- and far-infrared ranges. These crystalline silicates have many absorption peaks. The main peaks in forsterite at 10, 11, 20, 24, 34, 50 and 70 μm shift to longer wavelength and weaken as the Mg/(Mg + Fe) ratio decreases. We discuss the composition of cometary dust grains in relation to our data.