Take this lovely rainbow piece. It's almost exclusive found in a place called the four corners region of the Colorado Plateau in the USA where the states of Arizona, new Mexico, Utah and Colorado touch. It's dinosaur bone, petrified, permineralized or replaced with agate-type compounds. The original bone material has been replaced so that the structural detail is preserved and the interior pores and cavities have been filled with silica or quartz cystals letting us see the unique cell structure of once living dinosaurs.
There is a wide variety of colours from dull brown which looks like dino poop to these gorgeous specimens which look anything but. It all depends on the impurities that were in the surrounding sediment, chlorite, chromium, iron-oxide and manganese being some. The pink piece is extremely rare.
Of course non-gem grade fossilized dinosaur bones are found in many places around the world.
But only a small portion has everything needed for a fine piece to be made into jewellry like these from Mark Anderson.
These specimens have not been raided from official sites as it's illegal to collect dino bone on US state for Federal lands. Most of the bone available is in broken blocks and chunks which due to erosion, weathering, and method of deposition, the pieces are not associated with a complete dinosaur skeleton and are of little value to a paleontologist
But the colours of gem quality Dino Bone are worth looking at and it is Jurassic Age material dating from 136,000,000 to 145,000,000 years old.