Holmquistite is a lithium magnesium aluminium inosilicate mineral with chemical formula: Li₂(Mg,Fe²⁺)₃Al₂Si₈O₂₂(OH)₂. It crystallizes in the orthorhombic crystal system as prismatic crystals up to 10 cm or as massive aggregates. It has a Mohs hardness of 5-6 and a specific gravity of 2.95 to 3.13.