The majority of the technical and scientific information pertaining to commercial calcined kaolinitic clays of the type metakaolins (MK) are currently focusing on the pozzolanic reactivity and replacement of Portland cement. It is not adapted for geopolymerization and sometimes irrelevant. The aim of the present paper is to propose a customized test on metakaolins for geopolymer formulations. Standard commercialized Na and K silicate solutions with MR=1.7 were mixed with eleven commercial metakaolin samples (MK) and hardened at 80 °C. The temperature increase was recorded and the cumulative exothermal peak temperature is used to characterize very precisely the geopolymeric exothermicity of each commercial MK. In the Geopolymer standardized method, the geopolymeric exothermicity is expressed as the time in minutes it takes to reach the exothermal peak and its temperature, namely from the fastest to the slowest commercial MK: Metaver SF (21 min., 103 °C) – Argical M1200 (22 min., 103 °C) – PowerPozz White (26 min., 103 °C) – MetaMax (27 min., 103 °C) – MK Argeco (30 min., 93 °C) – Argical M1000 (34 min., 106 °C) – MK Pink (34 min., 106°C) – Metaver I (45 min., 100 °C) – Metaver M (50 min., 93 °C) – Metaver N (>60 min., 82 °C) – MK 1300 (>60 min., 80 °C).

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