Mercury Ores

Abstract

The mercury ores in Idria were named empirically after their appearance and mercury content. These names were preserved through the centuries of mining. A detailed classification of Idria ores was given by SCOPOLI (1761) and HACQUET (1781), who described dozens of varieties, mainly related to sedimentary ore types. Here we introduce only the most common ones. Sedimentary-exhalative ore bodies are emplaced in the upmost part of the mineralized strata. They formed by the exhalation of brines into shallow marine swamps in form of thermal springs. In a reaction with sulfide ions released under reducing sedimentary conditions chemical precipitation of cinnabar-opal slurry took place. It was deposited alternatively with colloform pyrite in the layers of clastic material. Unconsolidated cinnabar-opal slurry was transported by the turbid flows, forming various layered ores (MLAKAR and DROVENIK 1971). In sedimentary ores, the ore minerals serve as a binder of clastic material and form continuous monomineralic layers. Mercury exhalation in the Langobardian period was accompanied by an intense volcanic activity, which contributed a large fraction of clastic material into the sedimentation basin.