The search for magic opal was successful. This is evidenced by the order of Emperor Rudolf II, addressed to Stefan Kecer of Pekľany, ordering him to make his land accessible to the mining of precious stones. This written document confirms that the opal mine by Červenec is officially the oldest one in the world. Until the discovery of other opal deposits in Mexico and Australia, it was the only known mining site in the world until the 19th century.