What is Whitby Jet?
Whitby Jet is the name given to the black resinous material found within the Jet Rock Series group of black laminated shales which forms part of the Upper Liassic rocks of the North Yorkshire coast. These rocks date from the Lower Jurassic Period, making them some 180 Million Years old. When examined under a microscope, Whitby Jet can be seen to be a fossilised wood, which has been compressed due to the pressure of the over lying sediment. Although most literature reports the tree species to be Araucaria - similar to the modern monkey puzzle, we now believe there to be multiple species involved.
The jet occurs at random horizons within these shales in planks, rather than seams making locating it problematic. The lack of bacterial decay in the jet suggests that it was deposited very quickly. Sand grains embedded in the jet implies that it was once a driftwood resting occasionally on sand bars as it made its journey from the forests, down rivers and eventually into the sea where it became waterlogged and sank to the sea bed. It is suggested that the Lower Jurassic was an era of particularly severe weather conditions with the coastline being repeatedly buffered by hurricane grade storms which stripped the trees from the landmass which would explain the relatively frequent deposition of driftwood.
The original wood of the trees was replaced soon after deposition by complex organic molecules preventing the silicification of the remains. As a result Whitby Jet has a light almost plasticky feel. It is a relatively soft material being 3.5-4 on Mohs hardness scale (diamond is 10) but is surprisingly durable making it suitable even for rings. Whitby Jet has a vitreous lustre and unsurpassed depth of colour and can be likened to looking into a pool of oil, in fact when worked the jet smells strongly of oil.
In the Whitby are there is a marked difference in the quality of jet we find. Only the jet from the Jet Rock Series strata should be used for jewellery and is referred to as Hard Whitby Jet. This material is both chemically and thermodynamically stable guaranteeing the finished jewellery will last for potentially thousands of years as in the case of Roman Whitby Jet artefacts. The other shales in the Whitby are also yield jet but this material is less stable and prone to cracking and crazing. We refer to this material as Soft Whitby Jet.
Jet-like materials occur in many other localities world wide. Most collectors of jewellery have heard of Spanish Jet, which like our Whitby Jet is generally of excellent quality and is formed in a similar way to Whitby Jet. Most other "jets" however are found to be sapropelic coals, in other words are the result of the fossilisation of stagnant pools and are seen under magnification to be rich in plant spores. As a result they bear non of the gemmological qualities of Whitby or indeed Spanish Jet. In recent years the British market has been infiltrated by Siberian and Georgian Jet sold unfortunately as Whitby Jet. Hopefully further research into our Whitby Jet will enable us to legally protect our native material once an for all, a task our Victorian counterparts tried and failed to achieve following the threat to their trade from Spanish Jet.
In the meantime, ask lots of questions from the retailer before purchasing a piece of jewellery, most craftspeople in Whitby can be seen working the jet that they have collected themselves or bought from their trusted collectors. At the Ebor Jetworks we are always happy to show our source material, we only use the best quality Hard Whitby Jet in our jewellery but we are always happy to show examples of other jet materials and explain the differences in the quality of the types available.
Jet has a rich history of usage in Britain and by the start of the Bronze Age, jet artifacts amongst grave goods are widespread.
Jet finds increase in abundance into Roman deposits and although the Romans had a source of jet from Turkey, they had discovered jet in Britain by 3rd or 4th Century AD. Major jet pieces have been found in Eboracum modern day York which was founded in AD71 and a jet workshop, with partially finished items was uncovered near the present day railway station (hence we are not the first Ebor Jetworks!).
When the Roman Eboracum became Viking Jorvik in the 9Cth AD it was one of the most important trading centres in Western Europe and many jet items have been found from this era.
Through Medieval times and into the 19Cth jet was used only for ecclesiastical ornament such as crosses and rings, this was all to change however with the Victorian preoccupation with mourning. With the death of George 1V in 1830 the Lord Chamberlain's Office issued a decree that stated that "the ornament will be jet", and in Whitby, jet production went into overdrive. With the death of Prince Albert in 1861 Queen Victoria led the whole country in mourning.
By 1873 there were 200 shops manufacturing in Whitby employing 1500 men, the value of trade being some FFD100,000, a million pounds by today's standards. However by 1880 the trade was already starting to decline mainly due to the use of poor quality soft jet, foreign imports and imitations. Sadly by 1921 only 40 men were still producing, dropping to 5 by 1936 and by 1945 there were 3.
After the First and Second World Wars, the nation was tired of mourning and everything associated with it was shunned. Failing to exploit new styles and fashions the industry could not go on. With the death of the last Victorian jet worker in 1958 the skills of this great era were lost. All modern day jet workers, of whom we number only a few, are self taught and few are as skilled as our Victorian counterparts.