Abstract: The crystal structure of macphersonite (Pb4SO4(CO3)2(OH)2, Pcab, a = 9.242(2), b = 23.050(5), c = 10.383(2) Å) from Leadhills, Scotland has been determined to an R = 0.053. The structure has many features in common with its polymorph leadhillite including three distinct types of layers. Layer A includes sulphate tetrahedra, Layer B is composed of Pb and OH, while Layer C is composed of Pb and CO3 with topology identical to that in cerussite. In both macphersonite and leadhillite these layers are stacked along  as ...BABCCBABCC... The double CC layer is almost identical in the two structures and forms a structural backbone and occurs in other structures including hydrocerussite and plumbonacrite. The sulphate layer shows the greatest difference between the two structures and can be described by a pattern of up or down pointing tetrahedra. For macphersonite the sequence along  is ...UDUDUD... while in leadhillite the sequence along  is ...UDDUUDDU... This latter sequence effectively doubles b relative to the equivalent direction in macphersonite. Susannite, a third polymorph, may have yet another sequence of sulphates to give trigonal symmetry; by heating leadhillite, displacive movements of sulphate groups may occur with a conversion to susannite.