In the Tiefer Stollen (deep adit), oolithic limonite, a mixture of hydrated iron oxides, was mined. The limestones of the Dogger, the middle Jurassic, are locally called Brauner Jura (brown Jurassic) because of their typical colour, which is caused by brown iron oxides. The amount of iron which is necessary to colour the limestone is very low. Some layers contain a very high amount of iron oxide which made the mining profitable during the 19th century.

The pure air of the adit is used for speleotherapy. In a separated chambers people with lung diseases visit the mine for medical treatment.