galloplumbogummite

Galloplumbogummite was discovered on a specimen from the second oxidation zone that had been bequeathed to the Mineralogical Museum of Hamburg University by Professor Hermann Rose (1883-1976). Galloplumbogummite, IMA 2010.088, is a member of the alunite supergroup and was named for its structural and chemical relationship to plumbogummite (Schlüter et al. 2014). Type material is conserved in the collection of the Mineralogisches Museum, Universität Hamburg, Germany (catalogue number TS 315).

The type specimen is from the second oxidation zone at Tsumeb and presents as colourless rhombohedral crystals of galloplumbogummite (to 0.15 mm), with frosted-white sides, in 2 mm-sized vugs in massive germanite-renierite ore associated with chalcocite, Cd-rich sphalerite, galena and pyrite (Schlüter et al. 2014). Galloplumbogummite crystals are strongly zoned with substitution of Al/Ga/Ge, Pb/Ca and P/S; the Ga₂O₃ content ranges from 11.07-26.03 wt % (av. 19.64) and the GeO₂ content ranges from 1.56 -10.93 wt % (av. 5.93).

A second specimen was discovered in the collections of the Royal Ontario Museum in Toronto, in which white spherical aggregates of galloplumbogummite are associated with otjisumeite on germanite ore (Schlüter et al. 2014, citing a pers. comm. from M. Back and F. Neuhold).

(It is notable that a Ga-rich plumbogummite from Tsumeb was described by Mills et al. (2009); please refer to the Plumbogummite section.)

chalcocite; edwardsite; galena; germanite; gunningite; ktenasite; lauraniite; lazaridisite; libethenite; niedermayrite; otjisumeite; pyrite; pyromorphite; renierite; sphalerite