The pozzolanic activity and hydration properties of feldspar after mechanical activation were studied in this paper. The research of the pozzolanic activity of the feldspar powders revealed the pozzolanic activity could be improved by mechanical activation, and it was affected by the particle size, specific surface area, crystallization degree, alkali dissolution rate, and pozzolanic activity index. After 20 min of grinding, the pozzolanic activity index of the feldspar powders was >65%, which could be used as pozzolanic materials in cement according to the Chinese national standard GB/T 2847-2005. The activated feldspar powders possessed the basic characteristics of pozzolanic materials and could react with Ca(OH)(2) to form C-(A)-S-H gel in the presence of water at room temperature, showing hydraulicity. The results provided a theoretical foundation for the evaluation of the pozzolanic activity and hydration properties of the activated mine tailings containing feldspar. (C) 2021 Elsevier B.V. All rights reserved.