Whitby jet originally was in the form of monkey puzzle trees about 180 million years ago during the Jurassic period. As the trees eventually died some of them were taken into the water of rivers and eventually ended up in the sea. The trees then would become engorged with water and sink to the bottom of the sea. Over a period of time they will be covered by thick layers of sand and mud, which and compressed under the sheer weight of the water above. This enormous pressure over the millions of years caused what was the monkey puzzle tree to become the material we now call jet.

In Britain today the best place to find Jet is the Yorkshire coast around the Whitby area and it can actually be found at low tide.

After the death of Queen Victoria's husband Prince Albert in 1861Whitby Jet was very fashionable. The Royal Court considered appropriate to wear Whitby jet, in times of mourning.

Jet is a fabulous substance but there are a lot of other substances that look very similar. So I'll give you some ways of making sure you buy the genuine article, especially since Whitby jet as become quite expensive over recent years. So it's best to try and make sure that if you're going to buy some Jet you're buying the real material.

With the term "jet black" there is absolutely no doubt that jet is black in colour and if it's not totally black it's not jet. So that's the first way of testing, visually checking the colour in good light. If the Whitby jet has been polished it as a very nice sheen to it..

Secondly is to feel the jet itself, which should be light, most people expected to be heavier than it actually is and also it should have a warm feel to it.

There is a type of glass which has the term "French jet" but this is quite heavy when felt and as a glaring type of reflection.

You can even get modern types of plastic which can be mistaken for jet, but there are far too shiny usually with moulding marks which tell the tale of their origin.

There is one test which is called red hot needle test, but obviously it's usually very difficult to try and conduct this kind of testing, especially if you are stood in the shop looking at what is supposed to be Whitby jet. The idea is you heat up the tip of the metal and then touch it into the material which is supposed to be jet, if it is it will smell very similar to coal but will have a tarry smell to it also.

The best way to test if the material looking at is jet are not is the streak test. First of all you need a piece of analgise porcelain similar to the back of a ceramic tile, or a piece of sand paper and you scratch your material across it. If it is Whitby jet it should leave a dark brown mark, a piece of coal would leave a very dark streak.

If your substance is black in colour, if touched with red-hot metal smells of burning coal and most convincingly leaves a brown when rubbed, there is quite a good chance that you've got the genuine article of Whitby jet.

A short film of what Whitby jet is and how to tell if it's genuine Whitby jet