Barrow Museum wrote:
Yes, there is a way to differentiate between Jurassic bone (which you rightly note is the case for your fragment on account of its adhering limestone matrix). Try touching your lip with a bone fragment...if it is Pleistocene (Not Palaeogene at South Cerney), then it will stick slightly to the damp lip skin on account of its porosity - it has lost all its collagen but not been mineralised yet. A mineralised Jurassic bone won't stick, will feel heavier and harder with usually a darker colour. Just beware of modern bone which also won't stick as it still contains collagen (and was probably part of someone's dinner!)
A lot of Pleistocene mammal teeth, tusk and bone comes out of your local pits and you will probably remember the complete mammoth skull which used to be displayed in the Water Park visitor centre. If you have not found any yet, then keep on looking because it is there. If you do, then don't just let it dry naturally, but immerse it for at least a couple of weeks in a milky PVA suspension and dry it out very slowly, otherwise it will probably disintegrate.
I have collected Pleistocene bones that are only about 50 000 years old, and they are completely mineralised and as dense as your typical Jurassic bone from Lyme Regis or dinosaur bone from the Isle of Wight. Just because something is dense and well mineralised doesn't necessarily mean it is relatively old. Likewise, i have collected marine reptile bones that are over 100 million years old and they are still lightweight and porous like modern bones. It varies on a case by case basis.