In the last decades Egerszalók was famous for the white travertine mound and the non-stop and free small thermal pools which were popular meeting points of the local people. Nowadays a spa- and wellness hotel utilizes the unique thermal water. There are 17 indoor and outdoor pools in the hotel with 1 900 m2 water surface. The temperature of the water is 65 °C.
The De-42 thermal well was drilled as a hydrocarbon exploring well on the Demjén oil field in 1961. The Eocene limestone was dead ground for hydrocarbons but hot karst water was spouted from the well. As recharging hot karst water flows down the mound-side cools down and loses its carbon-dioxide content. As a result a bright white travertine cover evolves on the mound-side. Now due to environmental reasons the well is closed and a reduced recharge preserves the travertine reserve.
Currently the spa obtains thermal water from another well (De-42/a). This well recharges the limestone aquifer in great depths, as well.
The recharge area of the Egerszalók thermal wells is Bükk Mountains. Based on radiocarbon dating, it takes the precipitation water infiltrating on the Nagyfennsík (Great Plateau) to get to the Egerszalók wells 12 000 years. During its way, water gets to great depths in the karst aquifer, warms up and dissolves mineral components.
The water discharging from the well is middle mineral content Ca-Mg-HCO3-type hard thermal water with significant sulphur, carbon-dioxide, silica and fluoride content. Currently the total solid content of the water varies between 1100 and 1550 mg/l and the water temperature is around 65-70 °C. The water was certificated as medicinal water in 1992.
SMARAGD-GSH Ltd. designed the safety plan of the medicinal water in 2003.