The opal mines in Dubník (in the second half of the 19th century the designation Červenica-Dubník opal mines were also used) were known all over the world since the end of the 16th century because of the precious opal mined there. It is possible that opal was mined here already during Roman times. The opal mines experienced their most famous period under the family of the Viennese jeweler, Samuel Johann Nepomuk Goldschmidt, who settled in Dubník. Until the discovery of opal deposits in Mexico and Australia in the 19th century, opal mines in Dubník were the only mining locality in the world. In the post-war years, in 1922, mining was stopped at Libanka and other mining fields due to unprofitability. The underground of the opal mines was again accessible to the public from 1st July in 2015 through the Jozef adit.