Abstract: In the official records, copper mines in the southwest of the Qing empire seem to suddenly appear in the late 1730s. In part, this impression is an effect of government attention. Copper, which was the most important metal for casting cash coins, became a pressing concern when imports of Japanese copper dwindled. The government responded by developing domestic resources. Seemingly overnight, Yunnan mines reached impressive levels of productivity and replaced imports. For several decades, the Tangdan mines in northeastern Yunnan supplied most of the copper consumed by the centrally important metropolitan mints. The sudden boom is remarkable and not entirely plausible. This article reassesses the history of Qing-period mining by examining a particular case study. It explores an essay about the Dongchuan earthquake of 1733 that provides a glimpse at the empire’s leading copper mines on the eve of the recorded boom. A close analysis of figures, mining technology, and organizational structures reveals that the mines had been developed by mining entrepreneurs and migrant workers for a considerable period of time outside government attention, operating in a gray zone of unlicensed exploitation. The studied case permits a new assessment of the role of the state and of nonstate players in the industry. Moreover, it throws a new light on the image of Qing society and economy created by the official emphasis on agriculture and the actual role of the nonagrarian sector.