Along the way, you will learn about the "life" of this rock; from its origin at the water spring, to its extraction for commercial purposes in the former quarry, and its final use in local and world architectural projects.

Tufa is a biochemical sedimentary rock. If you look closely, you will see impressions of mosses, twigs, seeds, cones, leaves, grasses and even snail shells and tree trunks. It can be brownish-yellow, greyish or reddish in colour. The red colour comes from iron oxides. The rock darkens over time due to oxidation. In the central part of the quarry, you can see that water containing suspended clay particles from shale occasionally flows over the black shaley claystones and the tufa, staining the top layer black.

The water flowing in this part of the Karavanke mountains is acidic, as it is rich in carbon dioxide (CO2). The acidic water dissolves the porous limestone, but does not affect the claystone, which is why it flows where these two rocks meet. At springs, where the water flows to the surface, the carbon dioxide is released in the form of gas. Some of it is used by plant life, while the rest escapes into the air. The limestone that was previously dissolved in the water now hardens again at the surface. It settles on the pores of plants, animal remains and other organisms. Their soft parts eventually decay, but the imprints remain. The calcareous coatings of the former organisms now form a brittle, porous and pitted rock – tufa.

Due to its mechanical properties, tufa is very useful in construction and stonework. Tufa from Jezersko was once used for carvings, arches, window frames, portals and other ornamental elements for religious and other buildings. In recent times, its use has primarily shifted to interior and exterior cladding of buildings and for frescoes. Tufa can be found in many homes in the Jezersko area, and it also adorns many important buildings in Slovenia. It also form the arches in the Church of Our Lady of the Rosary in Kranj (pictured), designed by the world-famous architect Jože Plečnik.

The tufa deposits in the former quarry reached up to 18 metres of thickness, but most of the stone has now been quarried. Underlying the tufa is a much older impermeable black silty claystone (carbon). Due to water flowing between the shaley claystone and the tufa, as well as the claystone layers sitting relatively vertically, the thinner surface layers can often slide and threaten the road and the Kokra River. One of the landslides was triggered in the central part of the quarry, where layers of previously overlain black shaley claystone are now visible on the surface.