White crystals of the extremely rare Gallium-Germanium mineral galloplumbogummite (IMA 2010-088) from Tsumeb, the type and the only known locality worldwide. The specimen has a lot of microcrystals of white galloplumbogummite, associated to minoritary cleavages of silvery metallic gallite (another gallium mineral). Analyzed specimen, Galloplumbogummite is one of the great rarities of Tsumeb, and one the most sought after species from the locality. Only two of 5500 known minerals have at the same time Gallium and Germanium in its chemical composition, this one is one of the two (the other, krieselite, also from Tsumeb). — Photo: David Hospital · CC BY-SA 4.0
Galloplumbogummite
Galloplumbogummite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Pb(Ga,Al,Ge)₃(PO₄)₂(OH)₆.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Alunite-crandallite structural group.
Key properties: specific gravity 4.62; White streak; optically uniaxial.
IMA symbol Gpbg, IMA status: approved, named in 2010.
A secondary mineral derived by alteration of Ge-Ga minerals in the oxidized zone of a dolostone-hosted, polymetallic, hydrothermal deposit.
It is found associated with Germanite-renierite, chalcocite, Cd-rich sphalerite, galena, pyrite.
Reflects dominant essential gallium and the mineral’s structural relation to plumbogummite.