Speculating on the Sources of Tin for the Chinese Bronze Age

We propose that trace levels of gold found in early Chinese bronze objects derived from the added tin, and that tin minerals in north-east China, probably from placer deposits containing gold and cassiterite (SnO2), were the sources of tin throughout the Chinese Bronze Age. We investigate compositional data from over 300 unprovenanced ritual bronzes attributed to the Shang and Zhou dynasties and 138 bronzes unearthed in Anhui, Henan, Sichuan and Shaanxi from the Shang dynasty (c. 1500–1046 BC) to the Warring States period (475–221 BC). We consider that early bronze has low concentrations of gold because gold had been intentionally removed from cassiterite prior to smelting. We suggest that this time- and labour-intensive practice was generally highly developed during the Chinese Bronze Age, and perhaps any bronze age. Recognising that tin and gold can be found in the same metalliferous provinces, and that there was demand for both metals but not necessarily from the same groups of people, we propose a mechanism based on a symbiotic relationship between gold and tin that was maintained until placer deposits became exhausted and primary gold ores were mined in the first millennium AD. With evidence of early tin smelting and increases in the numbers of settlements, we propose that north-east China, with its rich deposits of tin and gold, is an increasingly viable candidate for the source of tin throughout the Chinese Bronze Age.