Known as živo sebro (living silver) in Slovene, legend has it that mercury was first discovered here at the end of the 15th century by a tub maker who witnessed it trickling out of the rocks in its native form while he was testing out one of his buckets in a small stream. Created in the form of mercury rich cinnabar ore some 235 million years earlier during a period of intense tectonic and volcanic activity, by 1500 a small mine and smelting plant had already been established, and thus began the extraction process that would continue for over 500 years.
The cinnabar ore found here is exceptionally high grade, with up to 78% mercury content, and over its five centuries of operation the mine produced a staggering 13% of all the mercury ever mined in the world - making it second only to the famous Almadén mine in Spain, which was active for nearly five times longer. During an exceptionally productive period at the end of the 18th century, the value of mercury from Idrija's mine accounted for 5% of the total economic output of the Habsburg Empire, an amount that is almost unfathomable by today's standards. Due to both local environmental concerns and falling international demand, the mine began a two-decade process of winding down operations, which included backfilling most of the 700km of shafts out of which 107,000 tons of mercury had been carried.
Nowadays visitors can visit the building that formerly served as the mine's main entrance, Anthony's Shaft, where they can watch a short video presentation explaining its history in more detail and take a tour through a section of the mine that is still open. In June 2012, the mercury mines of Idrija and Almadén were jointly recognised as official UNESCO world heritage sites.