One of my favourite finds from our last visit to North Yorkshire was a huge Whitby Jet trunk section measuring nearly a foot in length!! It is extremely rare to make a find like this especially having been sea washed out.
It’s a very interesting specimen for a number of different reasons and because of this I decided to leave it as natural as possible and have just polished it up on one side.
As you can see from the picture it polished up really well and looks stunning!
This specimen gives away a few clues as to how Whitby Jet is formed. It is not solid Jet all the way through but has a jet “skin” on the outside with the core being stone. From this we can deduce that the Jetionisation process starts from the outside and works inwards, most likely working through the trees rings. Something interrupted the process in this specimen, making the centre of the trunk solidify before the Jet could be created.
As you can see from the reverse side I have left this natural, you can make out that the tree had a knothole which has been nicely preserved (this is towards the top middle). There is also a faint ammonite impression on this side which I always love to see on Whitby Jet. These impressions occur due to the weight of the sedimental layers slowly increasing creating tremendous forces which push anything laying on top of the trunks (in this case a ammonite) down into the forming Jet.
As I said its a fantastic specimen of which I hope to conduct some further research on when I find the time! 😀