Cubanite , Maucherite , Valleriite Locality: Mackinaw Mine (Weden Creek Mine), Monte Cristo , Monte Cristo District, Snohomish County , Washington , USA ( Locality at mindat.org ) Size: 12.6 x 9.2 x 5.1 cm. A hefty ore specimen, with probably tons of material stuck inside it as well as what you see on the outside, judging by the look of it. I think the cubanite (and associated more rare species) fills thin fracture seams within. On the exposed main face, there are dozens of thin, flat-lying cubanite crystals to 7mm in size. Apparently this specimen was exchanged to the Academy by the Smithsonian. Ex. Philadelphia Academy of Sciences and Smithsonian Institution Collections. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Maucherite
A gray nickel arsenide crystallizing in tetragonal tablets among other nickel minerals in hydrothermal veins.
Intro adapted from Wikipedia (CC BY-SA).
Maucherite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ni₁₁As₈.
It crystallizes in the monoclinic crystal system (space group P4_12_12).
Key properties: Mohs hardness 5; specific gravity 8; Blackish gray streak; Metallic. Anisotropism: Weak. R1 –R2: (400) 44.2–44.8, (420) 45.1–45.4, (440) 46.0–45.9, (460) 46.9–46.4 luster.
IMA symbol Muc, grandfathered status — known before the IMA’s founding, named in 1913.
Found in hydrothermal veins with other nickel arsenides and sulfides.
It is found associated with Nickeline, nickel-skutterudite, chalcopyrite (Eisleben, Germany); millerite, uvarovite, pyroxene, calcite (Orford, Canada).
The mineral was named to honor Wilhelm Maucher (1879–1930), metallugical chemist and mineral dealer of Munich, Germany.