Austinite belongs to the adelite mineral group of calcium and lead arsenates, and has the conichalcite/descloizite type of crystal structure. The crystal structure of nearly pure austinite, CaZn(AsO 4 )OH, was redetermined (R = 0.014) and the absolute configuration identified. The space group P2 1 2 1 2 1 and cell parameters a 7.5092(8), b 9.0438(9), c 5.9343(8) Aa match previous data. Zinc octahedra share edges to form chains parallel to c. Arsenic tetrahedra share vertices with the Zn octahedra to generate a compact framework. Calcium square antiprisms share edges to make chains parallel to a that occupy the channels in the zinc-arsenic framework.