Introduction: spionkopite occurs in supergene alteration assemblages derived from primary sulphide mineralization in which copper is an important component. It typically occurs, in intergrowths with the other supergene sulphides, as replacements of the primary minerals, forming rims and veinlets along cleavage-planes and/or grain boundaries. Spionkopite is one of several non-stoichiometric copper sulphide species. By this it is meant that they have compositions which fit in between copper¹⁺ sulphide (chalcocite), and copper²⁺ sulphide (covelline). Many of these minerals are recent discoveries as they occur in complex, microscopic intergrowths which have required modern analytical techniques to unravel their detailed mineralogy. As a consequence, many previously studied assemblages containing 'supergene chalcocite' or covellite-like minerals may well prove to be a lot more complex: hence, further occurrences of spionkopite are likely to be unearthed.

Occurrence in Wales: unknown in Wales until relatively recently, spionkopite has now been found at two localities, one in North and one in Central Wales. These discoveries have both resulted from high-resolution reflected light microscopy studies of supergene alteration assemblages associated with the 'ore' in ancient (Bronze Age) copper mines.

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