Brianyoungite is a secondary zinc mineral. the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) classifies it as a carbonate with the formula Zn3(CO3)(OH)4,but sulphate groups SO4 also occupy the carbonate CO3 positions, in the ratio of about one sulphate to three carbonates, so other sources give the formula as Zn3(CO3,SO4)(OH)4, and Gaines et al classify the mineral as a compound carbonate.