An assessment of copper mineralization from the Great Orme Mine, Llandudno, North Wales, as ore in the Bronze Age

Abstract

SUMMARY Spoil heap and in situ mineralization from the Great Orme Mines, North Wales, have been classified into six mineral associations. By applying mineralogical, mining and beneficiation criteria, their probable exploitation as copper ores in the Bronze Age have been assessed. Major veins and open voids within dolostones are infilled by saddle dolomite–chalcopyrite–pyrite–calcite–malachite. The tonnage, estimated copper grade of 10% and continuity of the veins, plus the coarse grain-size of the copper-bearing minerals, suggest that the veins were mined in the Bronze Age possibly accompanied by contributions from adjacent void-infilling mineralization. Two minor types of mineralization, namely ‘copper ddu ore’, a very fine-grained, friable, limonitic vein-infilling, and disseminated, c. 1 cm diameter, azurite nodules in mudstones, may have been taken as a by-product of other mining operations. Neither the fine-grained, disseminated, Cu-, Pb-, Fe-, Co-, Ni-rich, polymetallic sulphides, which are only found in dolostones from the spoil, nor the single, copper-poor, but galena-rich assemblage found as a vein-infilling, can be considered to be Bronze Age copper ores. These last two associations belong to the Mississippi Valley-style lead–zinc mineralization of the North-east Wales Orefield that is older in age and differently sourced from the copper–dolomite association ores that produced Bronze Age copper metal. The recognition and sampling of ores, rather than mineralized specimens, from a mine site, have implications for geochemical or isotopic provenance studies that lie far beyond the Great Orme. This is because only run-of-the-mill ores should be treated as having any importance to archaeometallurgists.

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