The far‐infrared absorption coefficients of &agr; of 100 A˚ of a number of metals and also of amorphous and crystalline Al203have been measured at 4.2K and are orders of magnitude larger than effective medium calculations of &agr; which rely on bulk dielectric constants. These results complement earlier measurements on Al particles1. We find that: 1. &agr; varies linearly with filling fraction f for f?15% 2. The magnitude of &agr; does not depend to any great extent on whether the particles are free standing or are embedded in a KBr matrix, and 3. Particles of Au and Pd which do not form oxide coatings have larger absorption than do particles of Al or Cu with oxide coatings. A comparison of the resonance absorption in the visible part of the spectrum for Au and oxide‐coated Cu particles dispersed in KBr reveals that the key role of the oxide coating is to transfer oscillator strength from the far‐infrared to the small particle resonance in the visible.