Introduction: greenockite may occur as a primary mineral, associated with other base-metal sulphides, in hydrothermal mineral veins, or associated with calcite, prehnite and other minerals in vesicles in altered basic lavas (as in the type locality near Greenock in Strathclyde, Scotland). Supergene greenockite is commonly found as powdery coatings on fractures in weathered sphalerite, the latter mineral often being a significant cadmium-bearer. Some caution is required when identifying greenockite because it has a cubic polymorph, hawleyite, which when forming earthy coatings is identical in appearance.

Occurrence in Wales: the presence of 'greenockite' associated with weathered sphalerite in Central Wales has been generally known for some years (e.g. Jones & Moreton, 1977). However, specimens from the many localities require analytical confirmation to verify whether the substance present is greenockite or hawleyite, or even cadmium-stained smithsonite. Other similar localities have been noted in the Llangynog and Llanrwst lead-zinc (Pb-Zn) orefields. In the Halkyn-Minera MVT orefield there is a single record, but the smithsonite which commonly occurs in this area is sometimes a vivid yellow colour (see the smithsonite entry) due to the presence of cadmium. A more recent discovery was at Dolyhir Quarry in the 1990s: this is the most interesting (and the only confirmed) Welsh occurrence of greenockite in which the mineral occurs in a primary sulphide assemblage.

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