This habitat type includes springs where travertine – a porous sediment composed mainly of calcium carbonate – is formed. Travertine deposits when calcium-rich (hard, so to speak) groundwater seeps to the ground and evaporates. The non-evaporated water flows between the plants and into the upper layers of the soil, so springfens form around these springs as well: the travertine deposit is covered by well-decomposed peat soil. In the valley ridges, there is usually less than a metre of peat, but on a floodplain or at the foot of the ridge, the peat deposit can reach several metres. The vegetation cover is generally similar to that of calcareous fens (7210), and in some cases also to that of springfens (7160).
The petrifying springs are most common in the Sakala Uplands, but they are also abundant in the Otepää Uplands and Vooremaa.
Includes the habitat type 3131 (spring fen site type) according to Paal.