1.6" Goethite Pseudomorph after Pyrite - Egypt

This is a 1.6" wide goethite pseudomorph after pyrite and likely marcasite as well. This specimen was collected from the White Desert near Farafra Oasis, Egypt. These mineral aggregates have been collected for years from the Cretaceous age Khoman Chalk of the White Desert. Studies have been done to verify this mineral's composition, however the specific age of formation is unknown. While they're collected from a Cretaceous deposit, studies suggest that they formed post deposition.