Valorising mining waste is critical for sustainable resource management and reduced reliance on primary raw materials. Waste dumps from large-scale porphyry systems are potential secondary sources of critical raw materials (CRMs) as listed in Regulation (EU) 2024/1252. This study investigates mineralogical and microchemical heterogeneity in wastes from the Roșia Poieni porphyry copper district, Romania, testing the hypothesis that this heterogeneity governs both their secondary-resource potential and their environmental behaviour. Samples from the Geamăna and Halda Veche waste dumps were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and Raman spectroscopy. PXRD of five selected samples revealed marked inter-sample variability: chalcopyrite ranged from 12.88% to 13.48%, bornite and rutile reached 7.84% and 7.60%, and cuprite reached 15.78%. SEM-EDS confirmed Cu-rich bornite (55.25 wt.% Cu), while Raman spectroscopy identified melanterite alongside calcite and dolomite. The identification of pyrite, melanterite, and carbonate minerals suggests potential acid-generating and acid-neutralising processes, although validation by leaching tests and acid-base accounting is required. These findings establish a mineralogical basis for evaluating targeted recovery of critical and strategic raw materials alongside environmentally responsible mine waste management within a circular-resource framework; representative bulk geochemical analyses and recovery tests are still required to establish recoverable resources.