Formed by the coalification of individual Araucaria trees buried in Jurassic marine sediments, jet is mostly found in its durable ‘hard’ form. This can be carved into fine ornaments and polished, but a brittle ‘soft’ jet, with fewer ornamental properties, has also been worked.
Jet is not found in regular seams, but is randomly distributed throughout Upper Lias shales known as the Jet Rock. This is up to thirty feet thick and lies above the ironstone strata and below a freestone called the Top Jet Dogger. The Jet Rock outcrops on the coast from Ravenscar to Saltburn, on the northern escarpment of the Cleveland Hills and in the valleys. Drifts were driven at its base to the point where the shale became tougher. Known as the ‘face’, this was seldom further than 330 feet in. One man drove the drift, using a fine-pointed pick, while a second barrowed the shale to the surface where a third sorted it to find pieces of jet ranging up to five inches in thickness and six feet in length. By pulling down the drift roof, to form a platform, it was possible to work upwards through the shale until the overlying Top Jet Dogger was reached. This took very little timber, used no explosive and relied on natural ventilation. The work was lit by candles.
Jet has been used as an ornament for 4,000 years, and artefacts made from it have been recovered from burial mounds between Derbyshire and the north of Scotland. Nevertheless, it did not become popular until Queen Victoria endorsed jet jewellery on display at the Great Exhibition of 1851. After the deaths of the Duke of Wellington, in 1852, and Prince Albert, in 1861, the fashion of wearing jet during mourning gave the trade an annual turnover in excess of £90,000, and Whitby had over 1,500 employees in nearly 200 jet workshops, with the best carvers earning up to £4 per week by 1871.
While it was processed in Whitby, much of the jet was mined inland. For example, in 1871, Swainby had 38 miners, some of whom were locals, but others were unemployed ironstone miners. Agents, acting for the manufacturers, bought rough jet at the mines. It was then cleaned and sawn into blanks, of a various sizes, from which jewellery was carved and engraved with beautiful designs on its surface using knives, chisels and gouges. Finally, the work was polished on oiled boards, and finished by ‘rougeing’ over a spinning disc covered with walrus hide. Smaller pieces of jet were used to make beads, and intricate bits were finished on a brush wheel.
In the mid-1880s changing fashion and the use of alternative materials devastated the local trade. Traces of jet mining can be seen in many valleys in the North York Moors National Park, and along the escarpment between Guisborough and Osmotherley. Collapsed drifts and their shale tips are regularly spaced around the hillsides. A few have the remains of miners’ huts.
The shale, which contains about eight per cent oil, has sometimes been burnt to a rich red colour by spontaneous combustion, or through deliberately burning for use in road building. The latter practice, which could last for months, made a noisome smoke which was a nuisance to locals.
- Bower, J.A. “Whitby Jet and its Manufacture” Journal of the Society of Arts, 22, (19/12/1873), pp.80-87
- Cook, C.B. “Jet” in Butlin, R.A. (Ed.) Historical Atlas of North Yorkshire (Skipton: Dalesman Publishing Co. Ltd, 2003), pp.189-190.
- Hemingway, J.E. The Geology of the Whitby Area 1958
- Hemingway, J.E. (Ed.) The Geology and Mineral Resources of Yorkshire (Yorkshire Geological Society, 1974), pp.161-223.
- Kendall, H.P. The Story of Whitby Jet: Its workers from earliest times (1936)
- McMillan, M. Whitby Jet through the Ages (Published privately, 1992)
- Muller, H. Jet Jewellery and Ornaments (Shire Album No.52, 1994)
- Muller, K. & H. Whitby Jet (Shire Library)
- Owen, J.S. Jet Mining in North East Yorkshire (The Cleveland Industrial Archaeologist, No.3, 1975)
- Parkin, C. “On Jet Mining” Transactions North of England Institute of Mining & Mechanical Engineers, XXXI (1882), pp.51-57.
- Vickers, N. “The Structure of the Whitby Jet Industry in 1871”, pp.8-17
- Woodwark, T.H. Rise and Fall of the Whitby Jet Trade (1922), pp.10-11