The volcano is called „fossile“ because it became covered in younger sediments soon after its creation. It reached the surface again in the Pliocene (around 2 million years ago).
Gaveznica is located around 400 m south of St. Mary's Church in Lepoglava. In the past the name Kameni vrh was used for a steep andesite hill and Gaveznica was the lower area with the orchard of the Lepoglava penitentiary.
The name Kameni vrh was lost during the years and only the name Gaveznica remained in use. This area is known as the first agate finding site in Croatia. It is assumed that the Paulines used it in the Middle Ages, and evidence exists that it might have been used a lot earlier.
It appears that the Stone Age people knew it because stone knives, scrapers, stone axes and other tools were found in Vindija cave and the Great cave in Ravna Gora. In addition, green tuff hand chopping tools were found in Vindija cave.
Geological research showed that there are very few rocks made of quartz or other materials that might have been used for that purpose.
The colour of the agate varies from light blue to dark grey. Recently new finding sites of semi-precious stones were discovered near the village of Čret, 4 km east of Gaveznica. Some of them are various chalcedonies, red jasper and agate, although there is some amethyst and opal.
One more important thing ties Lepoglava to minerals and mineralogy.
The Gazophylaciun, an exceptional work of a Croatian Lexicographer Ivan Belostenec, printed in 1740, served as the source of the Croatian mineral terminology because it contains 270 terms belonging to the field of mineralogy. The first term found in it is the Achates, is. m3.p.p.