Wingeshausen - Bilsburg Thundereggs

Wingeshausen is a very unusual and rarely seen collection of German thunderegg locations. They are drastically older than the already quite old familiar German locations, dating from the Devonian period (350-400 million years ago). Their age may have something to do with the very bizarre cores that these often possess. Agate and Chalcedony is occasionally found here, in extremely weathered forms, but the majority of stone are filled with a range of other minerals, or are often completely empty, as though the core has long since worn away. Some have a metallic sheen to them. Of the three locations I am aware of, Schwarzbachtal and Steinhorst seem almost interchangeable, while Bilsburg is significantly different.