Róka-hegyi Kristály Cave

The Róka-hegyi Crystal Cave is one of the caves located in the Pilis Mountains in the Danube–Ipoly National Park, in Budapest District III. It is the most significant cave of the stone quarry on Róka Hill.

Description

The entrance of the cave is in the abandoned Róka-hegyi stone quarry’s southern rock wall, in a nature protection area. The unsealed, easily walkable cave can be visited without permission with basic caving equipment.

The cave formed at the boundary of Upper Triassic Dachstein limestone and Eocene marly limestone, along calcite veins, under phreatic conditions. By descending the entrance and climbing easily, one can reach a chamber 9 m long and in some places 2–3 m high. The chamber contains the end point of the cave. Large surfaces of calcite and dolomite are found in the cave, but these surfaces have become slightly damaged today. The old door closing the cave has broken down and this may have greatly contributed to the current state of the cave. It is the most significant and longest cave of the stone quarry.

The cave received its name because of the crystals occurring in it. In literature the cave also appears under the names Crystal Cave (Mezei 1967), Rókahegyi Crystal Cave (Leél‑Őssy 1958), Rókahegyi Crystal Cave (Jakucs, Kessler 1962) and Rókahegyi New Cave (Bertalan 1976). The nearby Róka-hegyi Cave also has name variants Crystal Cave and Rókahegyi New Cave.

Research history

In the study published in 1958 and written by Sándor Leél‑Őssy, this cave may be described under the name Rókahegyi Crystal Cave. According to the description, the entrance of the cave is in the large stone quarry at the northern end of Róka Hill, at about 220 m above sea level. At the cave entrance a large, characteristic spring‑funnel can be observed, which is clearly visible from a distance. It was opened by stone mining and the originally closed cavern was discovered. Part of the cave was mined, which is now about 30 m long and about 10 m deep. The characteristic spring‑water‑formed cave (old spring‑funnel) developed in Dachstein limestone. It is now heavily degraded, dry and becoming clogged. György Kertai wrote about the many pea‑stone aragonite crystals in the cave, which were deposited from the spring waters. The limestone in the cave powders heavily due to the spring‑water effect. A map sketch was attached to the study, showing the Kevély hill group. The map sketch shows the geographical location of the Rókahegyi Crystal Cave. In the drawing and the text the cave is marked with the number 1.

According to the 1962 Karst and Cave Exploration Bulletin, the customs guard cave exploration group discovered a new cave in the next stone mine west of the Róka-hegy cave. Its entrance, which is about 20 m below the summit, was opened due to stone mining. Through the narrow entrance the members reached an oval, chamber‑like pit 2–3 m wide and about 8 m deep. On the wall they observed dripstones growing on aragonite, among which was a dripstone 50 cm long. They considered it unusual that developing dripstones were present close to the surface. At the bottom of the pit, accessible through a narrow opening, there is a 2 × 3 m niche containing a small lake 1.5 m long and 50–60 cm wide. The formation of the lake was peculiar and therefore the lake was described in detail.

The description states that the lake bottom is undulating, veil‑like and covered with dripstones. The water level was constant because over the centuries the amount of water dripping from the walls and from above equaled the amount that seeped out and evaporated. The calcium concentration in the water constantly increased and therefore the deposition of dripstone occurred in a special way. The dripstone began to grow horizontally on the water surface, at its edges. In some places the dripstone reaches a width of 15 cm. At the edge it is 0.5 cm thick, snow‑white; on the walls it is three centimetres thick, light‑yellow. In the lake, in several places, small dripstone mushrooms grew, standing on thin stems on the lake bottom. The light‑yellow dripstone mushrooms, 3–4 cm in diameter, have a horizontal top and are as tall as the depth of the lake water. The lake was photographed from several points because the cave has no continuation and will be destroyed by mining. A similar formation resembling lake‑rose leaves is found in the Deményfalvi cave.

It first saw the light of day in 1962, and the book *World of Caves* states that the Róka-hegyi Kristály Cave opens in the large quarry above Csillaghegy. At the entrance of the very fragile karstic cave, remnants of a characteristic karst spring channel can be seen. Many pea‑stone formations have formed in the cave. According to the book *Pilis Guidebook* published in 1967, the Róka-hegyi Kristály Cave is located in one of the quarries of Róka-hegy, northwest of Csillaghegy. The Róka-hegyi Cave lies in the stone mine west of the Kristály Cave. The Kristály Cave is a long‑known cave of karstic origin, about 30 m long and about 10 m deep. Its walls are covered with many pea‑stone‑like formations.

The *Budapest Encyclopedia* published in 1973 mentions that from the depressions of the quarries operating or abandoned on the top and sides of Róka-hegy, two small (karstic) pits and several small artificial cavities open. The *Pilis Guidebook* published in 1974, in the list of caves of the Pilis Mountains and the Visegrád Mountains (pages 19–20), notes that the Kristály Cave lies between the caves of the Pilis Mountains and the Visegrád Mountains. The description of the Pilis Mountains caves matches the description of the Kristály Cave given in the guidebook published in 1967 that presents the Róka-hegyi Kristály Cave.