Do you know why we say "Jet
Black"?
Jet is a black semi-precious gemstone which is
actually fossilised wood.
Whitby jet was formed from trees very similar to the modern
day monkey-puzzle tree but which lived about 180 million years
ago during the Jurassic period. When the trees died they fell
into water in swamps or rivers and some were washed into the sea.
The trees would become waterlogged and sink to the bottom, there
to be slowly covered by thick layers of sand and mud. Over the
millions of years between then and now the tree remains were
compressed by the massive pressure of hundreds of metres of
covering which accumulated. As the sand slowly changed into
sandstone, the mud changed into either shale or mudstone and the
some of the tree remains changed into the substance we know as
jet. Movement and erosion of the earth's surface has finally
brought the Jurassic rocks back to the surface in some areas. The
best place in Britain for finding jet is the Yorkshire coast
around the Whitby area where small pieces can be found on the sea
shore at low tide.
Because jet is easy to carve (hardness 3-4 on
Moh's scale) and has a beautiful black sheen, it has been
used as a decorative stone since stone-age times. The Romans used
jet for decorative purposes and used the name gagates for
this stone. Jet is not unique to Britain, some of the earliest
artifacts have been found in Germany, but it can also be found in
Spain and in Utah and Colorado in the United States.
With the growth of rail travel and interest in
'holidaying' on the coast, Whitby became a popular
seaside haunt for the Victorians. The Victorians liked to collect
souvenirs of their holidays and from Whitby the treasure had to
be a piece of jet, the most popular item being a brooch,
sometimes carved with a name or love message. As this interest
grew so did the Whitby jet industry, in the 1830's there were
two jet shops in Whitby and by the 1870's this had grown to
over 200 shops. When Prince Albert died in 1861 Queen Victoria
entered into 'severe mourning' and would allow only jet
black jewellery to be worn at court. The Victorian people
followed this fashion and soon jet jewellery became the height of
fashion.
Because of its low hardness jet could be shaped
and carved by hand and earlier examples were produced this way
using home-made tools and files. Mechanisation soon reached the
jet industry and after initial rough shaping with chisels, jet
pieces would be shaped and carved using treadle driven rotating
wheels made of lead and coated with abrasive powder. Wheels
coated with woollen material or chamois leather were used along
with polishing powder to obtain the final finish. Lathes were
used to mass produce round beads for the chunky Victorian
necklaces which would then be patterned using the lead cutting
wheels.
Before the boom in jet sales most of the jet sold
had been picked up on the seashore. However demand for jet in
Victorian times far outstripped supply and mining for jet became
common. Remains of the old jet mines can still be seen along the
Yorkshire coast from Staithes to Robin Hood's Bay. Jet was
also mined inland where there were less problems with tides and
high cliffs. Modern day demand is less than in Victorian times,
mining for jet is no longer economical, and demand is now met
once again by the seashore.
Jet jewellery is still produced in Whitby. The
modern jewellery is less 'chunky' than the Victorian
jewellery and consists mainly of pendants, earrings and brooches,
usually with silver fittings.
Beware of fakes
The brooches pictured above are all fakes. The one on the left
is modern plastic, the centre one is Irish bog oak with a carving
of Whitby Abbey and the one on the right is vulcanite. All three
look like genuine jet but when examined closely do not have
lustre or feel of the real article.
The necklaces pictured above are also fakes. The
one on the left is 'French Jet' (glass), detectable by
its very cold feel compared with the real thing. The necklace on
the right is modern plastic, the clue to its identity are the
thin moulding marks on each bead, genuine jet is carved or cut on
a lathe and will not have the marks left by a mould.
The moral of the story is BE CAREFUL,
all that is black is not jet.
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