Abstract On Earth, silica‐rich volcanism is typically associated with convergent plate boundaries, yet Mars, a stagnant‐lid body, also hosts regions with silicic lithologies. Here, we introduce a novel approach to directly estimate bulk silica (SiO2 wt.%) using multispectral data and machine learning. Our results reveal that an exposed pluton within a crater in Syrtis Major exhibits notably higher silica concentrations (62–83 wt.%) compared to the volcanic rocks of Nili Patera (60–72 wt.%). This observation suggests the presence of dacitic lithologies in Nili Patera and rhyolitic compositions in Syrtis Major, indicating that Mars may have experienced multi‐stage magmatic crystallization processes akin to Earth. Furthermore, Nili Fossae displays diurnal variations in silica, with higher values in the afternoon and lower values in the evening (35–55 wt.% SiO2), consistent with ultramafic bedrock overlain by silica‐enriched dust. These quantitative estimates will enable quantification and mapping of various lithologies and provide insight into its compositional evolution.