d In this work, the leaching behaviour of six aluminosilicate industrial minerals and by-products (kaolin, metakaolin, fly ash, natural pozzolana from Milos, zeolite and furnace slag) in alkaline solutions is investigated. The variables studied are the kind of alkali metal (K, Na), the concentration of the alkaline solution (2.5, 5 and 10 M) and the time of dissolution (5, 10 and 24 h). The solid residue after the leaching was examined by means of XRD and FTIR. As it is concluded, the leaching ability of Al and Si is according to the following descending order: Metakaolin > Zeolite > Slag > Fly Ash > Pozzolana > Kaolin. The extent of dissolution is higher in NaOH than in KOH solutions, especially when the most reactive materials are concerned. Finally, Si and Al seem to have a synchronized leaching behaviour in both alkaline solutions.