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Jet FAQ

Introduction

Whitby is known throughout the world for its 'Jet' and the Museum holds an outstanding collection. Our curators and staff are frequently asked questions hence this FAQ which we hope will provide background information and answer most general queries. The curators and staff are happy to answer more detailed questions concerning Jet (note however that we NOT WILLING to value Jet items).

  1. What is Jet ?
  2. What sort of items were made from Jet ?
  3. Where can I see items made from Jet ?
  4. Where is Jet found ?
  5. How can I tell real Jet ?
  6. How were Jet items made ?
  7. Where can I find further information on Jet ?
  8. Where can I buy Jet ?
  9. How should I care for my Jet ?

What is Jet ?

Jet is a semi-precious gemstone of organic (i.e. it contains carbon) origin. The name is derived from the Greek Lithos Gagates which translates as 'Stone of Gagas'. Gagas was a town in Asia Minor (Turkey). This name passed into old French as Jaiet, and into English as Jet. Jet was formed from wood that fell into stagnant water and which then became fossilised in much the same way as coal was made. The wood originally came from trees similar to the modern day Monkey Puzzle or Araucaria. The original 'wood-like' structure of Jet is revealed under the microscope, sometimes to the extent that the annual growth rings of the trees can be seen. Two types of Jet are generally recognised : soft and hard Jet. The former was probably formed under fresh water and the hard Jet in sea-water.

Section 2 Section 1
Photograph of thin section of Jet. 120X magnification. Woody tissue which has escaped compression with granules of quartz Photograph of thin section of Jet. 120X magnification. Woody tissue which has been greatly compressed with particles of quartz.

It has a low specific gravity (about 1.3) and on Moh's scale of hardness both forms rank at 3 to 4. The difference between the two forms becomes apparent when worked with hard Jet being tougher and more durable. Like coal it will burn. It takes a high polish and is the origin of the phrase "as black as Jet". When rubbed on a piece of unglazed porcelain it leaves a brown streak. Being a poor conductor it is warm to the touch.

What sort of items were made from Jet ?

The earliest example of Jet was found in Germany and dates from about 10000 BC. Jet has been used in jewellery since about 1400 BC. Pieces of worked Jet have been found in prehistoric burial mounds and in the 1st Century AD Pliny ascribed a variety of medicinal properties to Jet. Jet has mainly been used in jewellery and ornaments ranging from brooches, cameos, beads, necklaces, earrings, crucifixes, busts, miniature furniture, chess tables and even small models of buildings such as Whitby Abbey. On a more practical basis Whitby Museum contains spindles of Jet used in spinning, a loom weight and a tray for visiting cards.

Pattern Book
Page from a typical pattern book
Jet Necklace
Typical necklace
made of Jet

Where can I see items made from Jet ?

One of the most important collections of Jet is found in Whitby Museum, but good examples can also be seen in the Yorkshire Museum, Castle Museum and Jorvik in York, in the Victorian Jet Works Museum in Whitby, in Sheffield City Museum and the Akiba Museum in Japan. Other Museums in Yorkshire and abroad may have one or two isolated examples as well.

Where is Jet found ?

Jet can be found in many countries, including France (Aude), Spain (Asturias), USA (Utah), Turkey, China, Germany, India, Poland and Russia. However Whitby is particularly famed for its high quality Jet.

Jet is found throughout the North York Moors and remains of Jet Mining can readily be seen near Great Ayton, in Bilsdale, Bransdale, the Esk Valley and on the coast near Kettleness and Saltwick. It occurs in the Jet Rock series in the Upper Liassic particularly in the upper part just below the top Jet Dogger. It occurs in thin seams or as nodules.

NYM Location Map

Jet was generally mined, though it can sometimes be picked up off the beach. The mines were run by small companies of up to 12 men and consisted of tunnels driven into the side of hills. These tunnels were about 1.8 m high by 1 m wide and the spoil was brought out in tubs or wheelbarrows. At the mine-face the miners used a pointed pick and shovel to loosen the jet. Explosives were rarely used because of the risk of damaging the jet. At the mine-face candles were usually used for illumination, though lanterns and oil lamps were used in some mines. It was then transported to Whitby to be made into jewellery and ornaments.

How can I tell real Jet ?

Beware of cheaper imitations often sold as 'Jet'. Ebonite or vulcanite, bakelite, black glass, coal, epoxy resins and other materials have all been used to imitate Jet. Most of these do not leave a brown streak when rubbed on a piece of unglazed porcelain though ebonite or vulcanite will. The definitive test is to use a red hot needle on some inconspicuous part of the item when a coal-burning smell will ensue. However be very careful not to destroy or damage the item, remember Jet will burn. A safer way is to closely examine the item in question - signs of moulding (rounded edges rather than the sharp edges obtained by carving) or fading in sunlight to a khaki colour are sure signs that the item is an imitation. Remember also that Jet is warm to the touch unlike glass for instance.

How were Jet items made ?

Jet can be shaped by means of knives, saws and files. However in the early 1800s mechanical means of turning, cutting and polishing were used. A special mud from Derbyshire was used to polish the jet. The very final polishing was carried out with rouge, a fine iron oxide powder using wheels made of wool, walrus or porpoise hide. Final finishing was carried out on a wheel made of chamois leather (like some people use to polish their cars!).

Jet Workshop
Interior of Jet Workshop photographed by Frank Meadow Sutcliffe

It is thought that the first Jet workshops opened in Whitby about 1808. By 1850 there were about 50 such workshops making jewellery and ornaments. In 1873 it is claimed that about 1500 persons were involved in the industry supported by about 200 miners. The industry reached a height of popularity in the UK in the late 19th Century due to the Victorian custom of mourning. When Prince Albert died in 1861, Queen Victoria wore jet jewellery as part of her mourning dress for several years. Many of the works closed down in the 1920s due to cheap imports, chiefly from Spain. Today there are only about a dozen people involved in making jet jewellery in Whitby.

Where can I find further information on Jet ?

Bower J A Whitby Jet and its Manufacture J. Soc. of Arts, 22, 19th Dec 1873 p80-87
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. p161-223
Kendall H P The Story of Whitby Jet 1936
McMillan M Whitby Jet through the Ages Published privately 1992
Muller H Jet Jewellery and Ornaments Shire Album No. 52, 1994
Owen J S Jet Mining in North East Yorkshire The Cleveland Industrial Archaeologist, No. 3, 1975
Parkin C On Jet Mining Trans. N. England. Inst. Min. Mech. Engrs. XXXI, 1882 p51-7

Where can I buy Jet ?

A few items of Jet jewellery can be found in most antique shops in Whitby, particularly those in Church Street.

How should I care for my Jet ?

Jet can be safely washed in a mild detergent and warm water. It is recommended that moistened cotton wool swabs be used to gently remove any surface dirt. The Jet should then be allowed to dry and then the 'shine' can be restored by gently wiping with baby oil. Always keep Jet separate from other jewellery since it is relatively soft and can easily be scratched. It is suggested that each piece should be wrapped in tissue paper to prevent rubbing against other items.