The invention relates to a hydraulic mineral composition which is characterized in that it comprises a vitreous or crystallised matrix based on magnesium and calcium silico-aluminates which represent at least 25 wt.-%, and preferably 30 wt.-%, of the composition, one or more mineral oxides and optionally one or more specific mineral halides which are selected from among the oxides and halides of Ti, V, Cr, Mn, Co, Ni, Cu, Pb, Ba, Sr, P, S, Na, K, Zr, Mo, Be, Tl, As, Sn and Cd and which represent at least 5 wt.-% of the composition, at most 31 wt.-% alumina (Al2O3), less than 10 wt.-% ferrite, and less than 0.05 wt.-%, and preferably less than 0.01 wt.-%, C in relation to the weight of the composition.