Senegalite with turquoise

Named in 1976 after its country of discovery, this rare hydrated aluminium phosphate mineral (the pale yellow crystals contained in the vug or cavities encompassed by the layer of blue copper phosphate). This specimen comes from the type locality, a magnetite iron mine called Kouroudiako. It is found in the oxidised zone at the top of the deposit, where the primary minerals have been altered by reactive fluids that passed through the deposit, probably as erosion brought it closer towards the surface and into contact with groundwater. The specimen measures 8 x 7 x 4.5 cm.


Image credit: Rob Lavinsky/