smithsonite

Closely intergrown modified rhombs (to 4 mm) of burnt-orange smithsonite on an indeterminate matrix, the reverse of which (Exhibit 2) hosts quartz crystals coloured bright red by inclusions possibly of cuprite (v. chalcotrichite), although this has not been verified. Under the stereo microscope minute orange-brown inclusions of iron oxides - possibly goethite (?) - are visible in the smithsonite crystals.

The specimen is from the collection of Clement Victor Latz which was donated to the Australian Bureau of Mineral Resources (now Geoscience Australia) in 1976. 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 2022; Southwood et al. 2025). They hypothesised that the burnt orange colour of the smithsonite is due to the presence of microscopic inclusions of goethite (?), supplemented by the partial oxidation of ferrous iron in solid solution in the smithsonite lattice. Analytical data is presented in Exhibit 3.

cuprite (?); goethite (?); quartz