This study investigates whether a naturally formed dry crust in sulfide-rich soil can serve as abarrier that limits oxygen and water penetration, thereby reducing sulfide oxidation, and isfunded by the Swedish Transport Agency (Trafikverket)t. Sulfide soils contain iron sulfides that,when exposed to oxygen and moisture, generate acidity and mobilize metals. In many miningenvironments, prolonged oxidation leads to the formation of hardpan, a dense, cemented layerdominated by secondary minerals such as Fe-oxyhydroxides and gypsum, which can restrict thetransport of water and oxygen. The present work examines whether the dry crust identified inÖverkalix, Sweden, exhibits similar properties.Soil samples were collected from the crust and analyzed chemically and mineralogically usingICP-SFMS, XRD, and SEM-EDS; the results were compared with those from previouslystudied acid sulfate soils (ASS). The dry crust contained very low sulfur but high iron andphosphorus, indicating nearly complete sulfide oxidation and extensive secondary mineralformation. XRD confirmed a silicate-dominated matrix with 4.5% ferrihydrite. SEM-EDSrevealed Fe-O-rich precipitates and accessory minerals, including REE-bearing phosphates.Compared with ASS profiles, the crust showed elevated As and Cu, consistent with strong metalretention by Fe oxyhydroxides.Despite high Fe content and fine-grained structure, the dry crust did not qualify as a hardpan. Ithad unusually high water content (~49%), lacked cementation, and could not be recovered as anintact monolith, rendering oxygen diffusion testing impossible. Its behavior suggests that whilethe crust can temporarily retain metals through adsorption and co-precipitation, rewetting mayremobilize them. Thus, although the crust shows characteristics favorable for potential barrierformation, it does not currently exhibit the mechanical strength or low permeability associatedwith hardpans. Understanding these processes, however, may help guide strategies tointentionally induce hardpan-like stabilization in sulfide-bearing soils.