9.9" Polished Dinosaur Bone (Gembone) Slab - Blue Core

Agatized or agate replaced dinosaur bone is a rare form of fossilized dinosaur bone where the original fossilized bone (typically permineralized with calcite) has been re-mineralized (replaced/substituted) with silica-type compounds (agate, jasper, chalcedony, or opal). In a unique and isolated circumstance, the strata on the Colorado Plateau were uplifted during the tertiary intrusions, about 35,000,000 years ago, when the San Rafael Swell and the La Sals, Henry, and Abajo Mountains were formed. As these ranges were forming, local strata layers were flooded with silica-rich, superheated groundwater. This provided the appropriate environment to begin the replacement of the calcite in the original fossils with silicates. The most prolific layers of gem bone come from the Morrison Formation which is late Jurassic in age.