White fibrous spheres of nordgauite and yellow crystals of rittmannite. Ex Jürgen Kastning collection. From: Silbergrube, Waidhaus, Neustadt an der Waldnaab, Upper Palatinate, Bavaria, Germany. — Photo: Leon Hupperichs · CC BY-SA 3.0
Nordgauite
Nordgauite is an IMA-recognized mineral species in the phosphate class, with the chemical formula MnAl₂(PO₄)₂(F,OH)₂·5.5H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Nordgauite structural group.
Key properties: specific gravity 2.35; White streak; Earthy, slightly waxy to silky (aggregates) luster.
IMA symbol Ndg, IMA status: approved, named in 2010.
A late stage secondary hydrothermal mineral in altered zwieselite-triplite masses in a zoned granite pegmatite.
It is found associated with Apatite-(CaF), sphalerite, uraninite, a columbite-tantalite phase, metastrengite, whiteite-jahnsite (inclusions).
The name refers to Nordgau, the oldest name for that part of northeastern Bavaria in which Hagendorf is situated, and where mining has taken place since the 13th century.