What is jet?
Whitby Jet is considered a gemstone and has been used through history to make jewellery and other items. Jet comes from trees as does coal. In the case of Whitby jet the wood came from the ancient ancestors of modern pine trees. It was buried in the presence of salt water and with pressure and heat became jet. Whitby jet is nearly 200 million years old and was mined both on the coast and inland. Nowadays you can still find Whitby jet by beachcombing on the Yorkshire coast. Anyone can find it if they keep looking. Jet is found in a few other places around the World but the top quality hard Whitby jet is considered to be among the best in the world.
It is important to understand that there is no exact scientific definition of what is Whitby jet. Some of what is sold on line as Whitby jet would probably not be classed as Whitby jet by some of the Whitby jet workers.
The problem on the shore
The big problem is that there are many coal seams to the North of Whitby and hundreds and thousands of tons of coal waste was dumped over the cliffs in the Durham coalfields as well as that which the sea eroded from the land. This means that after any storm you will find lots of coal washed up. So you have black coal and black jet with much much more of the former usually.
How can you tell its Whitby jet?
With experience you can often guess from a distance that it might be jet by its shape and shininess. The best check is to rub a corner of the black stuff on a piece of pale sandstone or better still a pale piece of fine wet and dry. I find the best wet and dry is Mirka Carat in the fine grades as it is a very light gray color so shows up the colors better. If the streak is black it is coal if ginger brown it is jet. The best jet is quite hard compared to coal and leaves quite a pale brown streak (cinnamon color) on the fine grade wet and dry as in the larger two pieces below. The bottom right piece is coal giving a black streak.
However you find many pieces of the black stuff that appear hard and shiny and will polish. They give a streak somewhere between the black and the ginger brown streak. What are they? Possibly poor quality jet or maybe some type of hard coal. Maybe cannel coal. You may find all the above sold as Whitby jet on the internet. If buying a piece of rough jet on the internet I would ask to see what sort of streak it leaves. If it is not light brown then walk away.
Just to confuse us, some material looks very like jet and seems hard. It will polish and it gives a ginger streak. It looks black when you first pick it up but tends to have browny bits on it when it dries out as in the photo below. Is there such a thing as brown jet? Or is it slightly softer with some surface browning. Does Whitby jet have to be jet black! Sorry I do not know.
The big Whitby jet imposter.
There are other materials which are similar to jet which you might come across. You are most likely to mistake cannel coal for jet. It is a shale with organic material in it, a type of oil shale. It can be shiny and have a very similar form and hardness to jet. This means in shape it often looks the same. It gives a black streak . Cannel coal has also been used to make jewelery. It is nearly as hard as jet and has been used to make jewelery since neolithic times. Cannel coal is relatively common. It lights easily and burns well without a smoky flame. It was prized as a coal for open fires. People find this and are convinced it is jet.
Where you find jet?
Basically anywhere you see black stuff washed up on the Yorkshire coast. More is washed up in the various bays along the coast where the sea tends to deposit material. The areas around Whitby such as Staithes, Runswick bay and Robin Hoods bay are well known for finding jet. They are near the deposits and so are are obvious targets. Even if the weather has not been good you may still find a small piece or two that others have missed.
However a few places further South can on rare occasions be good as well.
The jet, like coal, only just sinks in salt water so is easily carried along by the sea. The basic flow of material along the Yorkshire coast is from North to South. This means anywhere along the Yorkshire coast has jet on the beaches at some time.
One or two of my biggest pieces have actually come from the Southern part of the Yorkshire coast. Some of these clearly had no signs of erosion from the sea so had probably just come out of the eroding boulder clay cliffs. Boulder clay is what the ice sheet left behind having ground down from the North. I have found lumps of coal still stuck in the boulder clay cliffs probably from the Durham coal fields. No reason why some jet has not traveled in the same way.
I did talk to one professional jet collector who said he had found jet still stuck in boulder clay.
If you find a piece of jet search close by very carefully as jet is a very slightly different density to coal and so tends to get sorted together by the sea. Although there still may be a a lot of coal near it.
There are some people along the coast who do collect jet to sell to the jet workers still in Whitby or with online shops. They know the various places it gets washed up and after what sort of conditions. Jet collectors will use the whole of the Yorkshire coast not just round Whitby.
As you walk you may see holes in the cliff which I think are old places that jet was mined. Some may still try and prize it out of the cliff. I think highly dangerous and probably illegal. I would not risk it.
You will not be the only person looking for it and you may not be the first there. Sorry but I am not telling you my favorite places.
When to find jet
After the sea has had a good stir up is the best time. This means after any gale from north west round to south east and even better if the gale coincided with strong tides. The sea often deposits and then sorts stuff better just after the gale. We do have more gales in Winter.
After an Easterly gale in winter when there are big tides is therefore the best time. Obviously you need to be there as the tide is going out.
Unfortunately we can get several years when we do not get these ideal conditions. However you can still find jet throughout the year anywhere you can see patches of coal washed up.
Do read our section on beachcombing and read about wash ups. There is some useful information there.
Value of Whitby jet
The best quality hard Whitby jet that is properly black and leaves a pale brown streak does have some value. Many pieces are quite small but really large pieces can be found. They are very rare.
A really good website to find out more about jet is the Ebor jet works
Polishing Jet at home
You do not need expensive equipment to polish jet. I use fairly common DIY tools but you will have to splash out on some polish and fine wet and dry abrasive and of course you may not have some of the tools I had. I used the following.
- Coarse then fine paper on an orbital sander. I actually held the sander in a vice with the abrasive paper uppermost and pushed the jet down onto it. Be carefull you don’t clamp the sander too tight or you will break it.
- Fine wet and dry (400 grade)
- Polished it with blue polish on a buffer wheel. I actually bought a rat tail to fit onto the end of my bench grinder and a soft buffing wheel.
- I finished some of the more intricate details with a dremmel type tool with a very small buffing wheel
You could put a buffing wheel on an electric drill. Clearly if you have no powered tools you could do it all manually.