smithsonite

A matrix of sooty grey-black corroded sulphide is almost completely encrusted by well-formed crystals of near-colourless smithsonite. The smithsonite crystals resting directly on the matrix are simple rhombohedrons, but many of the later (?) crystals are larger (to 15 mm) and elongated, with combinations of prism and rhombohedron. These larger crystals have a very subtle pink blush. Microscopic incusions of relict sulphide (?) are visible in many of the crystals. A few very tiny (c. 0.2 mm) quartz points are visible on some of the sulphide surfaces.

The specimen was purchased in 2014 from an Australian collector but there is no record of provenance or location in the mine.

The specimen has been analysed by EMPA-WDS and LA-ICP-MS as part of a study of the causes of colour in smithsonite (Weall 2023; Southwood et al. 2025). They hypothesise that the very weak pink blush in the smithsonite is due to Co (99 ppm) which is just at the threshold required to influence color. There is insufficient Mn (247 ppm) to participate in color formation. Analytical data is presented in Exhibit 2.

quartz