mawbyite

Mawbyite is a member of the tsumcorite group of minerals, and was first described in 1989 from Broken Hill, New South Wales, Australia (Pring et al. 1989). Visually, mawbyite is readily confused with carminite (of which it is the monoclinic dimorph) or with sewardite. Quantitative analysis is required for certain identification.

Specimens of "red tsumcorite" were found at Tsumeb in the 1970s and 1980s (Pinch and Wilson 1977; Keller, 1984). Gebhard (1999) suggested that "… red tsumcorite may represent the mineral mawbyite" but he was unable to offer proof at that time.

The first analytical verification of mawbyite from Tsumeb appears to have occurred in 2004 (Terry Seward, pers. comm. to Rob Lavinsky, 23/12/2004). The best specimens, believed to be from the second oxidation zone and possibly from 30 Level (?), comprise rich but partial encrustations of red, sub-mm mawbyite crystals on tennantite-rich ore, with etched, tan-coloured wulfenite crystals (to 6 mm). An excellent example of this paragenesis is conserved in the Pinch Collection at Harvard University (MGMH 2020.7.742).

Curiously, Von Bezing et al. (2016, citing an undated pers. comm. from Ted Immelman) noted the occurrence of "… small yellow-brown crystals …" of mawbyite on scorodite. This paragenesis (or similar) is also represented in the Pinch Collection by a specimen on which a siliceous matrix with quartz crystals is encrusted by red-brown mawbyite crystals associated with blue-green scorodite (to 6 mm) and sparse tabular wulfenite crystals which are orange and transparent (MGMH 2020.7.684).

gaitite; hematite; quartz; scorodite; wulfenite