Bayldonite is a copper-lead arsenate occurring in the oxidation zone of copper-bearing deposits and is named after English physician John Bayldon. It forms green, yellow-green, dark green to green-black, subtranslucent crystals with a resinous luster. More commonly, it occurs as massive, fine granular to powdery and also as crusts and minute mammillary aggregates with a radial fibrous structure. At Tsumeb, bayldonite forms a beautifully contrasting rich green background for other colorful secondary minerals such as azurite. It is found abundantly associated with azurite, mimetite, cerussite, anglesite, malachite, olivenite, duftite, schultenite, and beudantite at the Tsumeb mine, Tsumeb, Otjikoto Region, Namibia; Dioulasso, Allier, France; and at the Frijole prospect, Santa Rita Co., Arizona, USA; and Penberthy Croft mine, St Hilary, Mount's Bay district, Cornwall, England, UK, the type locality.
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