In this work, the potential of reflectance spectroscopy for the qualitative and quantitative analysis of a large number of heterogeneous secondary products (slags, sludges, dusts, etc.) of the iron and steel industry was investigated in the context of dump site exploration. The ranges of visible light, near and shortwave infrared as well as mid- and longwave infrared were analysed comparatively. As a result, the spectral differentiability of a large number of by-products was demonstrated utilising principal component analyses as well as other clustering and classification methods. The spectral properties of these materials have been extensively characterised. Furthermore, it was demonstrated that various relevant chemical parameters of these materials can be spectrally predicted with a promising accuracy for screening applications. Thus, significant potential of corresponding data and methods to support dump exploration was demonstrated.