Dufrénite

Attractive radiating dufrénite crystal aggregates on matrix from the classic Wolf Mine in the Siegerland ore district, western Germany. The specimen features lustrous brown to dark olive-brown dufrénite forming fan-shaped to fibrous radial groups with a strong vitreous to silky sheen, well contrasted against the darker host rock.

Dufrénite is a hydrated iron phosphate and belongs to the phosphate mineral group. At the Wolf Mine, it occurs as a secondary mineral, formed during the oxidation of primary iron-bearing sulfides and phosphates within hydrothermal iron ore veins. Its development is closely tied to late-stage, low-temperature alteration processes in the supergene zone.

The Wolf Mine is a historically important locality for secondary phosphates and arsenates in Germany and is well known among advanced collectors for fine radiating dufrénite specimens. Most material was recovered during historic mining operations and subsequent collecting from mine dumps, with little to no modern production.

Dufrénite is considered uncommon, and well-developed radiating crystal groups of cabinet size are distinctly desirable. The mineral is moderately sensitive to humidity, as prolonged exposure to moisture can affect surface luster over time; dry storage is recommended.

Typical associated minerals at this locality include beraunite, strengite, rockbridgeite, vivianite (altered), goethite, and quartz, reflecting the complex phosphate assemblages of the Siegerland iron deposits.