Bayldonite Locality: Tsumeb Mine (Tsumcorp Mine), Tsumeb , Otjikoto (Oshikoto) Region, Namibia ( Locality at mindat.org ) Size: 5 x 4 x 3.5 cm. This is a complete-all-around, radiating spray of glistening, sparkly, grass-green bayldonite that has completely replaced a mimetite cluster. It dates from the first oxidation zone, 1890s-1910s at the latest. Ex. Sussman and Dr. Georg Gebhard Collections. This Photo was Mindat.org Photo of the Day - 16th Jul 2008 — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Bayldonite
A rare secondary lead-copper arsenate long attributed to Cornwall's Penberthy Croft Mine, though the provenance is unconfirmed.
Intro adapted from Wikipedia (CC BY-SA).
Bayldonite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₃PbO(AsO₃OH)₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 4.5; specific gravity 5.24–5.65; Resinous luster; optically biaxial.
IMA symbol Bay, grandfathered status — known before the IMA’s founding, named in 1865.
A rare secondary mineral found in the oxidized zone of some polymetallic deposits.
It is found associated with Mimetite, olivenite, azurite, malachite, tsumebite, cuprian adamite, duftite, keyite, schulténite, philipsbornite (Tsumeb, Namibia); beudantite, anglesite.
The mineral was named to honor John Bayldon, English physician who collected the original specimens.