Froschschacht

Last Reminder of the Diepenlinchen Mine

The chimney-like structure of the frog shaft is the most significant relic with a visible connection to the ore mine Diepenlinchen. Unlike all other shafts still present underground, this weather shaft is recognizable by its well-preserved and still visible structure today.

Due to its round shape, this shaft structure bears a strong resemblance to a short industrial chimney. The weather shaft served to ventilate the underground tunnels and drifts. The name “Frog Shaft” likely derives from “am Frösch,” as this was how a concession mentioned in the records of the mining surveyors from 1820 was referred to, where two men were employed.

The purpose of the frog shaft is to discharge used air (waste air from the outgoing mine workings). Through ventilation, the CO₂ that continuously escapes from the limestone of the mountain body is carried away, which would otherwise lead to deadly gas concentrations, particularly in the deeper parts of the mine. The shaft initially had a depth of 252 m and was later deepened to 360 m following further expansions.

The chimney of the frog shaft was restored in 2020.

In principle, cold and heavy fresh air sinks, while warmer and lighter exhaust air rises. To ensure good ventilation, there are at least two methods:

The old method: On the bottom of the frog shaft, a fire was maintained using old mine wood, which intensified the natural chimney effect of the outgoing weather shaft.

The more modern method: Warm air was supplied to the above-ground frog shaft chimney through a brick tunnel that was man-high, fed by a weather stove located in an outbuilding. Remnants of the man-high tunnel can still be seen today at the foot of the frog shaft.

In the early days of the mine, the fire at the shaft bottom was probably the simplest but also the dirtiest solution. However, as the mine quickly developed into one of the most modern ore mines, a weather stove was installed, which was fueled with old wood. Its task was to warm the fresh air that had previously serviced the individual operational points, thereby facilitating its faster evacuation through the air shaft.

(Text: Jens Mieckley)