Hydroxysodalite (H-SOD) microcrystalline particles were synthesized from basalt powder rich in calcicplagioclase (anorthite) by alkali activation at 80 degrees C/24 h. Sodium hydroxide (NaOH) solution was used as alkaline activator. The reactivity of the natural solid precursor basalt was studied using differential scanning calorimetry (DSC), and a maximum reaction enthalpy of (-Delta H) of 170 Jig was obtained. The chemical, mineralogical, and textural properties were obtained by using X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N-2-adsorption-desorption measurements. The synthesized material has a specific BET surface area of 20.5 m(2) g(-1) approximately 200 times higher than raw basalt material (0.1 m(2) g(-1)). The compressive strength of basalt based H-SOD/sand composite samples cured at 80 degrees C for 24 h upon using different amounts of the activator (NaOH) was evaluated under dry and saturated conditions. The dry samples with NaOH/basalt mass ratio of 0.12 have reached a compressive strength of 57 MPa. Wet samples, on the other hand, showed a compressive strength of 25 MPa after seven days of soaking in water and four episodes of wetting and drying. The present work illustrates that crystalline H-SOD could be synthesized from cheap basalt powder precursor. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.