Recently formed arsenates from an abandoned mine in Radzimowice (SW Poland) and the conditions of their formation

Abstract

In the mining galleries of the abandoned Au-As mine in Radzimowice, diverse groups of secondary arsenates crystallized recently. They form several characteristic assemblages. In the first of them the typical minerals are bukovskýite and melanterite. The second group of secondary arsenates includes scorodite, kaňkite, zýkaite, and pitticite. The third assemblage includes Co-Ni-Mg arsenates of the erythrite-annabergite-hörnesite series. The first assemblage crystallized in a zone with a very high activity of sulphate and arsenate ions and where the pH varies within a narrow range of 2.0–3.5. The second group of secondary arsenates formed in the acidic zone. The minerals identified here suggest pH variation within fairly wide ranges, from about 2.0 to 5.5. Contrary to the first and second mineral assemblage, the Co-Ni-Mg arsenates formed under different geochemical conditions. Their crystallization took place under weak acidic to neutral conditions.