Compositional segregation and solid solution in the lead-dominant alunite-type minerals from Broken Hill, N.S.W.

A study of the composition and unit cell data of a suite of lead-rich minerals of the alunite-jarosite group from the oxidized zone of the ore body at Broken Hill, New South Wales, Australia, has revealed almost complete XO₄ (X = As, P. S) solid solution in these minerals at this deposit. The species in the group noted are hidalgoite, hinsdalite, beudantite, segnitite and plumbogummite. These minerals at Broken Hill exhibit a number of growth textures, including oscillatory zoning, colloform handing and replacements. Zoning in these minerals is due to the segregation of Al- and Fe-rich members, and compositions indicate a strong coupling of Fe³⁺ with AsO₄^3- and Al with PO₄^3-.