Lukrahnite Locality: Tsumeb Mine (Tsumcorp Mine), Tsumeb, Oshikoto Region (Otjikoto Region), Namibia Picture width 0.5 mm. Analysed specimen. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Lukrahnite
Lukrahnite is an IMA-recognized mineral species in the arsenate class, with the chemical formula CaCuFe³⁺(AsO₄)₂(OH,H₂O)₂.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Helmutwinklerite structural group.
Key properties: Mohs hardness 5; specific gravity 4.18; Light yellow streak; Dull for aggregates to subadamantine on fracture surfaces luster; optically biaxial.
IMA symbol Lkr, IMA status: approved, named in 1999.
Secondary in the oxidation zone of polymetallic sulfarsenide deposits.
It is found associated with Beudantite, adamite, conichalcite, wulfenite, chalcocite, quartz.
The mineral was named to honor geologist Ludger Krahn (b. 1957), who provided the initial specimen for study.