Illegal Mercury Trading in Idria in the 18th Century
A large mercury deposit was discovered in Idria (Idrija) in the Slovenian karst formation at the end of the 15th century. From 1575 to the First World War, the mine was owned by the Austrian sovereign princes. Until its closure in 1992, it supplied roughly 13 % of all mercury mines and therefore its output is only exceeded by the mine in Almadén in Spain. Mercury was mainly used for amalgamation in the extraction of precious metals from their ores; goldsmiths used it for fire gilding, pharmacists as a remedy against syphilis, farmers used to try and heal their sick cattle.
The metal won from cinnabar was sold at good prices; therefore miners and other inhabitants of the region around Idria kept stealing the ore and smelted metal to gain additional income through its sale. In 1778/79, the authorities launched an extensive campaign against these thefts. Dozens of people were interrogated and a widespread network of connections came to light.. In the end, four of those accused were hanged; this harsh treatment was to act as a deterrent in future.