In the Kopolnó stream valley are the free quartz crystals that János Bányai mentions in local history and mineralogy literature under the name Ojdula diamonds. Balázs Orbán already mentioned the Ojdula diamond when he wrote: "The Kopoló valley, in which Ojdula is located, branched into two parts, penetrates far into the snow, into the valley of the streams and into the neighboring mountains, there are many wild ones. diamonds (very beautiful rock crystals), which are known as Ojdula diamonds and were featured in ancient boglar jewelry.” Diamonds are the size of a pea, have a fine edge and are polygonal in shape. These diamonds are more likely to be found after rain, when flowing water channels wash away accumulated deposits of yellowish-brown clay.

The elders say that many people found diamond grains in Ojdula, which they sold to Jewish merchants for good money. These diamonds are not suitable for polishing because of their dust and fragility. Ojdula diamonds can often be seen in rings. Tradition remembers a Count Nemes, who distinguished himself at the Viennese court by his jewels composed of large quantities of diamonds from Ojdula.