Sky blue mbobomkulite crystal aggregates associated to an unknown grass green mineral from the type locality in Mbobokulu mine (Mbobo Mkulu Cave, Nelspruit, Ehlanzeni District, Mpumalanga Province, South Africa) and only one of the two known localities worldwide. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Mbobomkulite
Mbobomkulite is an IMA-recognized mineral species in the nitrate class, with the chemical formula (Ni,Cu)Al₄(NO₃,SO₄)₂(OH)₁₂·3H₂O.
It crystallizes in the monoclinic crystal system. It is a member of the Chalcoalumite structural group.
Key properties: specific gravity 2.3; optically biaxial.
IMA symbol Mbb, IMA status: approved, named in 1979.
A rare product of oxidation and leaching of Ni–Cu from sulfides in the cave roof, reacting with aluminum from phyllosilicates and nitrate from bat guano (Mbobo Mkulu Cave, South Africa); in a sedimentary U–V deposit (Jomac mine, Utah, USA).
It is found associated with Allophane, chalcoalumite, hydrombobomkulite (Mbobo Mkulu Cave, South Africa); oswaldpeetersite, cuprite, antlerite, goethite, lepidocrocite, hydrombobomkulite.
The name refers to the Mbobo Mkulu Cave, South Africa, the mineral’s first-noted occurrence.