Knowledge of the water distribution in mantle lithosphere is important to model the evolution of cratons over time and the inner Earth water cycle. Attempt to estimate deep lithosphere water content from ‘water’ in nominally anhydrous minerals (NAM) from mantle xenoliths has been extensively used in the past. However, the ability of xenolith to preserve water signatures from deep lithosphere has never been fully demonstrated.In this talk, I will address this question through the example of a natural case study from the French Massif Central. The case study will be used to demonstrate the limits of the approach. It will also illustrate the perspectives opened up by the study of spectral signatures to identify lithosphere heterogeneities. These perspectives will be explored at global scale in the last part of the talk.