Agatized dinosaur bone is a rare occurrence where the original fossil bone has been remineralized and replaced with silica-based compounds such as agate, jasper, chalcedony, or opal. This agatization process occurs when fossil material undergoes uplift, which causes landmasses to rise and fold or crumple, creating plateaus or mountain ranges. These folded and crumpled layers are then flooded with silica-rich, superheated groundwater in conditions perfect for the replacing calcite in the original fossils with silicates. This is what happened to much of the agatized dinosaur bone found around the Colorado Plateau: these fossils were subject to this process as the Rocky Mountains rose about 35 million years ago.

These pieces of bone have been cut and polished to reveal their beautifully preserved internal cell structures. They come from a private quarry near Dinosaur, Colorado and are bone fragments/pieces that are either found on the surface from bones that were long since destroyed due to weathering, or from a layer in the quarry full of tumbled and broken bone fragments representing an event layer. Because they are isolated fragments, they may have come from any of the fauna of the Morrison Formation, though sometimes the dinosaur type can be narrowed down based on a piece's cell size and general shape.

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