Mellite, also called honeystone, is an unusual mineral being also an organic chemical. Chemically identified as an aluminium salt of mellitic acid, that is, aluminium benzene hexacarboxylate hydrate, with the chemical formula Al2C6(COO)6·16H2O.
It is a translucent honey-coloured crystal which can be polished and faceted to form striking gemstones. It crystallizes in the tetragonal system and occurs both in good crystals and as formless masses. It is soft with a Mohs hardness of 2 to 2.5 and has a low specific gravity of 1.6.