Solids experience smaller vibrations than liquids or gases. Given a molecule composed of N atoms, there are 3N - 6 normal modes of vibration. Each of these constitutes a fundamental vibration. These overtones normally are weaker. They tend to produce rather diverse and complex spectra.
Some spectral troughs come from fundamental vibrations, while others come from overtones.
The figure below shows mainly vibrational absorptions for several silicate and sulphate, non-metallic minerals.