The Lierbachtal Valley, near to the village Oppenau, was offering best conditions for the rockhounding on lithophysae. Because of devastations made by collectors at the finding locations, no more digging or collecting is allowed from the farmers on classical locations, such as the well known “Holzplatz”. Only housebuilding operations or road construction work are offering new findings. The lithophysae do occur in quartz-porphyric rocks, situated in a wheathered greyish-white soil. Their shape is globular to discoidal with an irregular skin, often decorated by little globes. They are presenting different structures and agate-types in their center:

- concentrical oriented sickle-shaped cells as part of the lithophysae are distinctive for the location.

- Sometimes several lithophysae are building a chain-shaped aggregation.

- Besides multicoloured fortification-agate a greenish not banded chalcedony (Plasma).

- Fortification-agates are occuring in combination with “water-level-agates”.

The place of discovery Niedermättle represents the Lierbachtal in a lot of agate-collections as finding-area. The cause is that into the 1990ies  a very large excavation produced here an enormous amounts of Lithophysae (Thundereggs).