2.15" Goethite (Limonite) Pseudomorph after Marcasite - Egypt

This specimen was collected from the White Desert, near Farafra Oasis, Egypt. These mineral aggregates, known by many as "Prophecy Stones", have been collected for years from the Cretaceous-aged Khoman Chalk of the White Desert. Studies have been conducted to verify this mineral's composition, but the specific age of formation is unknown. While they are collected from a Cretaceous deposit, studies suggest that they formed post deposition.