Zinc 锌, 白铅 or 倭铅

Zinc was the latest of the main metals that metallurgists extracted and recognised as a metal. It is silverfish-grey and brittle and not much use.

Zinc ores are relatively common and not infrequently found together with copper, iron, silver and lead ores. For this reason, metallurgists encountered zinc early on, but for a long time considered it another ore component that hindered the smelting of their targeted metals difficult. This is due to the low melting and boiling points of zinc, at 419.53 °C and 907 °C respectively. At the temperatures required for smelting most other metals and liquefying slags, zinc evaporated. It was known as a white substance that condensated in the upper part of furnace, in fact zinc oxide, and as the ore calamine, in fact zinc carbonate. Zinc oxide was mainly used for medical purposes, while calamine was smelted together with copper to produce brass.

Zinc distillation in retorts was discovered in India and practiced on an industrial scale at the famous Zawar mines from the 13th century on. Zinc distillation requires the separation of ore and fuel and an environment which catches the vaporised zinc without allowing it to oxidasee in the process. This was done by using ceramic retorts with a closed lid. The retorts were placed upright and had a catching bowl in the lid that caught the zinc as it solidified again at the end of the process.

According to Chen Hailian’s research, the distillation process was again invented in the mining region of Shanxi 陕西 in northwestern China, probably around 1500, where retort smelting had a longstanding tradition since the Song period (Chen Hailian 2017).

Zinc in the Far Southwest

The beginnings of zinc exploitation in the investigated region are unknown. Zinc mines apparently were suddenly in existence in northwestern Guizhou 贵州 and probably in adjacent areas of northeastern Yunnan 云南 by the early 18th century, when the Qing 清 government needed zinc for casting brass coins. Since mines with annual outputs of 1000 tons upwards do not materialise overnight or in a matter of years, zinc exploitation can be safely assumed to go back at least to the late Ming 明 or the early 17th century.

Ming records on medical substances of the late 16th century record calamine for Yunnan and Guangxi 广西 (Chen Hailian 2017, 259), and also mention that “sweet furnace stone” (luganshi 炉甘石), which may be zinc carbonate scraped out of furnaces or - by extension – calamine, was worked in central southern Yunnan.

Zinc mines that undoubtedly worked ores can be identified in Qing records. The by far most productive mines were located in northwestern Guizhou. Several mines were also worked in northeastern Yunnan, in fact in the border area with Guizhou. We have also identified 4 major zinc smelting sites in northeastern Yunnan which certainly go back to the first half of the 19th century and may have been worked into the 20th century. The largest two of these sites do not appear in the Qing records (Huangmukuai 黄木块 and Yinchangpo 银厂坡 in Yiliang 宜良, Qianchang 铅厂 and Laoqianchang 老铅厂 in Qiaojia 巧家县).

As zinc was a cheap metal, exploitation prioritised ease of access to ores and transport out of the mining areas. Rich karst ore deposits which probably permitted exploitation to focus on calamine and relatively feasible distances of 150-350 km of mountain roads to the Changjiang 长江 river system presumably led to the concentration of zinc mining in northwestern Guizhou and adjacent parts of Yunnan.

Research objectives

This project aims to pursue field research on the zinc mining region. A systematic survey of mining and smelting sites will serve as a basis for analysing the spread of the relatively recent zinc metallurgy and the sequence of exploitation for different metals in the area.