‘Alluvial gold’ in Bronze Age Egypt and Nubia: from placers or clasts, and why it matters

• ‘alluvial gold mining’ has two meanings, but only in the context of archaeological studies of Bronze Age Nubia. • proposed clast mining in Nubia contrasts with alluvial placer mining dominant in goldfields globally. • alluvial placer mining of detrital gold can yield artefacts containing PGE alloys. • ‘alluvial clast mining’ only yields gold like the source lode, hence no PGE alloys. • PGE alloys are common in Bronze age gold artefacts, so placer mining was the dominant mining method. We highlight a significant divergence of opinion within the research community focussed on Bronze Age Nubia, about alluvial gold mining processes. Some interpret ‘alluvial gold mining’ in the globally accepted context to describe placer mining, which is the recovery of detrital gold particles simply by washing or ‘dry-blowing’. Placer mining also recovers other heavy minerals and can yield gold containing platinum group element (PGE) alloy inclusions if (and only if) primary sources for gold and PGE exist in the drainage catchment, so that they can be co-deposited into placer deposits during turbulent water flow. By contrast, other researchers interpret ‘alluvial gold mining’ or ‘wadi workings’ in a globally unique way, namely the visual recognition and selective extraction for processing of distinctive gold-bearing quartz fragments from alluvium, while discarding the rest. We call this ‘alluvial clast mining’. It yields gold that mimics the source lode and will lack PGE alloy inclusions unless present in the gold lode, which is unlikely and contrary to universally-accepted interpretations. Hence, although inclusions of PGE alloys in gold artefacts are generally interpreted to indicate an ’alluvial gold’ source, in fact only one of the two forms of alluvial mining, namely alluvial placer mining, can yield these. Since PGE alloy inclusions are common in Bronze Age Egyptian gold artefacts then some or all host gold was sourced by alluvial placer mining , as alluvial placer gold , from a catchment containing a primary PGE source. If inclusions are absent, both the source and mining method are equivocal: from primary gold lodes; from alluvial clast mining; or from placers in locations without a PGE source. Precise terminology matters.