Fossilized dino bone
Dino bones from the Jurassic
These special stones are fossilized bones of dinosaurs from the Jurassic era. The bones are filled with agate by permineralization. In many cases the original bone structure is still nicely visible.
The Colorado plateau in Utah USA is the source of these special fossils. Strips of broken bone fragments from 156 to 146 million years old have been found here. From the fragments it is often no longer possible to determine from which dinosaur is was. But famous inhabitants of that time were: allosaurus, apatosaurus, brachiosaurus, diplodocus, stegosaurus and the tyrannosaurus.
Researchers assume that the dinosaur bones were initially preserved by calcite fillings. 35 million years ago, during the formation of a number of mountain ranges in the region, warm silica-rich water was pumped up through the bone-layers. This caused the calcite to dissolve and be replaced by agate. This process took place 100 million years after the death of the dinosaurs.