20 Eur 2014 - The Dubník opal mines conservation area -> Proof

The old opal mines of Dubník in eastern Slovakia, in the northern part of the Slanské Hills, were established to extract world renowned deposits of precious opal – the most beautiful gemstone found in Europe. Until the discovery of the opal fields in Mexico and Australia in the 19th centrury, Dubník was the only site of opal mining in the world. The Dubník mines were developed mainly between 1845 and 1880, when they were leased to the Goldschmidt family of Vienna. The largest precious opal to come from the Dubník field was found in 1771 at the surface. It weighed 607 grams and was named Harlekýn. Opal mining at Dubník ended in 1922, but efforts are currently being made to reopen the mines despite the failure of previous attempts to do so. The extensive mineworkings have become a wintering site for 16 species of bat, including the Geoffroy's bat, for which they are the most important known wintering site in Slovakia. In 1964 the Dubník mines were categorised as a conservation habitat, and in 1964 they were recategorised as a conservation area. Since 2004 the Dubník mines have also been classified as a Site of European Importance for nature conservation.