Brown crystals of the very rare mineral neustadtelite from the type locality (Güldener Falk Mine, Schneeberg, Saxony, Germany) and one of the few known localities worldwide. — Photo: David Hospital · CC BY-SA 4.0
Neustädtelite
Neustädtelite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Bi₂Fe³⁺(Fe³⁺,Co)₂(O,OH)₄(AsO₄)₂.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Medenbachite structural group.
Key properties: Mohs hardness 4.5; specific gravity 5.81; Light brown streak; Adamantine luster; optically biaxial.
IMA symbol Neu, IMA status: approved, named in 1998.
Found in vugs in quartz collected on waste piles from mining activity.
It is found associated with Cobaltneustädtelite, quartz, preisingerite, “limonite”/goethite, mixite, zeunerite, bismutite, bismutoferrite.
The name is derived from the locality, Schneeberg-Neustädtel, near where the studied samples were collected.