smithsonite

A druse of intergrown rhombohedral smithsonite crystals (to 12 mm), orange-brown in colour, with slightly curved crystal faces. Reddish-brown inclusions of iron oxides (?), possibly goethite (?), are visible under magnification. The smithsonite shows a moderate red fluorescent response to short wavelength UV radiation.

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 hypothesised that the colour of the smithsonite is due to partial oxidation of ferrous iron in solid solution in the smithsonite, supplemented by the presence of discrete Fe oxide inclusions. Analytical data is presented in Exhibit 2. It is noted that the chemistry is very similar to that of specimen TSNB512.

goethite (?)