Bones from the jurassic age are partially agatized, very heavy and sturdy specimens. These bones come from dinosaurs some 150 million years ago. The organic material of the bone has been replaced by agate and other minerals .When many bones are found of the same animal, scientists have given us a window into the past detailing what the dinosaur may have looked like when alive. Going through this work many different species of dinosaur have been found and identified and made our museums very popular and knowledgeable. Collectors worldwide are eager to own a piece of a dinosaur and that is why you see Two Guys Fossils offering these fossils for sale.