AbstractObjectiveIn the present study, we describe the features and functional properties of a new powder cosmetic ingredient, an amorphous mesoporous magnesium carbonate (MMC, also named Upsalite®) with regard to physical characteristics as well as functional attributes.MethodsPhysical and functional characterization of MMC, as compared to other common powder cosmetic ingredients (silica, mica, kaolin, talc and starch), was assessed using nitrogen gas adsorption, powder X‐ray diffraction, particle size distribution by laser diffraction, scanning electron microscopy (SEM), and oil and moisture uptake tests. The powder ingredients were also applied on human skin and analysed for short‐ and long‐term mattifying effect, and a new method was developed to measure flashback effect. MMC was tested for skin irritation using an in vitro cell model as well as in vivo, through the Human Repeated Insult Patch Test on 50 human volunteers.ResultsMesoporous magnesium carbonate has a high surface area and pore volume. It has an excellent absorption capacity and can take up both oil and water simultaneously. It provides instant and long‐lasting mattifying effect when applied on human skin without drying or irritating skin and exhibits no measured flashback effect.ConclusionMesoporous magnesium carbonate has good sensory and visual characteristics as well as excellent absorbing and mattifying properties, suggesting that it has great potential to replace other powder ingredients currently used as fillers and absorbers in powder cosmetics.