By an appropriate processing of the pyritic ashes (resulted as residue in the fabrication process of the sulphuric acid) can be valorised the metallic elements. The paper presents the magnetic characteristics of the powders before and after the thermal annealing, and also the flowability and the granulometric characteristics of these powders. Starting from a very low magnetization, σ = 3.65 emu/g, the Fe amount of the powders is dramatically increased, after an appropriate thermal treatment, to approx. 34 %, corresponding to σ=128 emu/g. The Fe-enriched powders, embedded in epoxy resin matrix, generate a composites material, which can be used as electromagnetic shields, based on their materials properties (permittivity, permeability and electrical conductivity) in the 1000 – 2500 MHz range.