Secondary minerals, and mixtures of Fe-Al compounds such as oxohydroxy and hydroxosulfates can be naturally generated from mine water in response to oxidation /bio-oxidation, mixing, evaporation and neutralization processes. Deposits observed in significant quantities, with very high iron content, from the mining perimeters of Certej-Coranda, Rosia Montana, and Boita Hateg were sampled and characterized. Schwertmannite and Goethite can function as adsorbents after drying or further processing. In both cases, the chemical analysis of the product is important in order to promote it to potential users. A preliminary evaluation of the adsorption capacity for As(III) was performed for the original material and for products obtained after calcination. Depending on calcination temperature, adsorption capacity decreases, and a leveling effect can be observed, most probably due to pore sinterizing and transformation to hematite, irrespective of the initial mineral.