Mbobo Mkulu Cave, South Africa
Speleothems: chalky powder
Frequency: Rare
Other geologic settings: In clays or lignites, formed by the reaction of sulfate-bearing solutions from the decomposition of marcasite or pyrite at moderate temperatures with aluminous silicates
First description of cave occurrence: Martini, J.E. 1980. New cave minerals, mbobomkulite, hydrombobomkulite, sveite, etc. South African Speleological Association Transvaal Section Newsletter 1: 20-28 Martini, J.E. 1993. A concise review of the cave mineralogy of southern Africa. Proceedings of 11th International Congress of Speleology, Beijing: 72-75
First description of non-cave occurrence: Haberle, C.C. 1805. IV. Flóz- Trapp- Gebirgsarten. in Beitráge zu einer allgemeinen Einleitung in das Studium der Mineralogie Berlage des Landes - Industrie - Comptoirs, Weimar: 262 (335)
Other cave locations & References: Cottonwood Cave, Guadalupe Mts., New Mexico, USA: Polyak, V.J. & Provencio, P. 1998. Hydrobasaluminite and aluminite in caves of the Guadalupe Mountains, New Mexico. Journal of Cave and Karst Studies 60(1): 51-57 Great Salitrari Cave, Cerna Valley, Romania. Onac, B.P. et al. 2009. The relationship between cave minerals and H2O-rich thermal waters along the Cerna Valley (SW Romania). Acta Carsologica 38(1): 27-39 caves from Venezuela: Urbani, F. 2009. Venezuelan cave minerals: second review. Proceedings of 15th International Congress of Speleology, Kerville Texas: 345
dolomite
The cave is developed at the contact between a thick layer of Archean dolomite and an overlying chert breccia (which forms the ceiling of nearly all the rooms and passages of the cave)
The breccia represents the siliceous residue after karst dissolution of dolomite, and it is overlain in places by thin quartzite and by a continous black shale (with disseminated sulfides)
Age: Precambrian
Group: Sulfates
Chemical formula: Al2(SO4)(OH)4·7H2O
[According to the official IMA-CNMNC List of Mineral Names (http://nrmima.nrm.se/imalist.htm)]
Deposition and stability: The mineral derived from the leaching of alumino-silicates and sulfide contained in the roof of the cave
- Monoclinic