White prismatic crystals of the extremely rare germanium mineral otjisumeite, from the only known locality worldwide. Otjisumeite was labeled as RRR in Tsumeb II Gebhard book (Extremely rare, single occurrence with less than 10 specimens known). In fact, when this book was published (1999), only 2 specimens were known worldwide (p.275). Analyzed specimen. — Photo: David Hospital · CC BY-SA 4.0
Otjisumeite
Otjisumeite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula PbGe₄O₉.
It crystallizes in the triclinic crystal system.
Key properties: Mohs hardness 3; specific gravity 5.77; White streak; Greasy to subadamantine luster; optically biaxial.
IMA symbol Otj, IMA status: approved, named in 1978.
Found in cavities in oxidized germanium-bearing sulfides in a dolostone-hosted hydrothermal polymetallic ore deposit.
It is found associated with Tennantite, germanite, reniérite, chalcocite, schaurteite, siderite, calcite, quartz, gypsum.
The name comes from Otjisume, the Herero name for Tsumeb, Namibia.