The extraction of ore minerals from fine-grained flotation tailings is a commercially interesting but technologically challenging endeavor that needs to be supported by a full technical and economic feasibility study. A novel approach to such an assessment is introduced here. It is illustrated by the example of a historic tailing storage facility containing on average 0.2 wt% of Sn as cassiterite. Mineral processing test work identified flotation as a suitable technology route to recover this cassiterite. The viability of flotation was attributed to three material parameters, namely grade, liberation and particle size of cassiterite. These parameters were quantified for a set of ten exploration drill cores by chemical assay and mineral liberation analysis. For each of the three relevant parameters a suitable weighting function was defined that was applied to the entire data set. The data was then geo-referenced and combined to construct a 3D model illustrating a depreciated grade, i.e., the amount of cassiterite-bound tin that can realistically be recovered from the tailings. Results of the case study illustrate the importance of combining chemical grade data with quantitative mineralogical and microfabric information in any effort to objectively assess the residual value contained in industrial tailings or any other residue considered for re-processing.