PaSSTEL database is aimed at characterizing the optical response of geological targets ranging from controlled powders to complex slab rock samples. It mainly consists of visible-near infrared bidirectional reflectance measurements performed on natural mineral solid solution samples, involving pyroxene and/or olivine minerals, with controlled grain size ranging from 45 µm to 2 mm, with six defined granulometric classes. Samples are derived from natural volcanic products with diverse contents of rock fragments, monocrystals and glass, various shapes and surface aspects. Samples can be homogeneous (e.g., olivine) or heterogeneous, consisting of complex mixtures (e.g., pyroclastics), with matrix contributions.