Jet is a
semi-precious stone which, when polished, takes on an intense waxy lustre of
the deepest opaque black
hence the use of the term 'jet-black'` in literature since
The rich black colour never fades, and the shine which can
be achieved is such
that polished jet was even used
as mirrors in medieval times.
Jet comprises an unusually
pure and hard form of fossilised wood - more specifically
an ancient and relatively
abundant species of monkey puzzle tree - which occurs as thin
within a series of shale
rocks (known as the upper lias) which were laid down in the early
Jurassic era some 175-185 million years ago.
After these ancient trees had died and
fallen, they would in times of heavy rain and flood often be swept into
swollen rivers. On
their way downstream they would be tumbled and battered, with many of the trees being
broken up and/or stripped of their
Upon their eventual arrival
at the sea, the by now water-logged timbers would rapidly
sink into the black mud
sea floor, where they would over subsequent millennia
be overlaid with sediments comprised
of sand, mud,
and organic remains. It was the accumulated weight of both this sediment and
the water overlying it which exerted
the great pressure which, over millions of years and
in chemically-complex conditions, resulted in the flattening
and compressing of the wood
into jet. It is at this point that a distinction needs to be drawn between 'hard' jet and
'soft' jet; the former being
formed in saline and anaerobic conditions, and the latter
being formed in more freshwater
and aerobic conditions. Only 'hard' jet proper is suitable
for working into jewellery and ornaments, and such finest quality
jet occurs only in one
specific and particularly tough and compacted layer of the upper lias shales known as
The ancient lias sea offered
precisely the right conditions for the formation of jet, the
area of this sea' today
corresponds with the area of land encompassed by the North
York Moors National Park. Jet
not only occurs
beneath much of the Park landscape itself, but - more importantly and
accessibly - is also exposed in the cliffs
lying to the north-west and south-east of
the historic fishing town of Whitby in North Yorkshire.
The jet can be found ex situ as small fractured and water-worn pieces,
on beaches and trapped amongst
foreshore rocks, or less frequently in situ as thin
seams within the cliffs themselves.
Also preserved in the Upper Lias shales
are the fossilised remains of extinct
sea-creatures such as ammonites and belemnites, which,
if in close enough proximity, can
leave attractive impressions on the underside of
the jet itself.
History Of Whitby Jet
Jet has been collected and worked into
objects of personal adornment for thousands of years, with beads, buttons, earrings, and
belt-sliders having been found in Bronze Age burial sites throughout the UK. Once Bronze
craftsmen discovered that the act of polishing jet caused it (by virtue of its
electrostatic property) to be able to 'magically' attract chaff, straw, and sawdust to
itself, jet became valued not only for personal adornment, but also
as a powerful bringer
of good fortune.
Romans made extensive use of jet during the early part of the first millennium AD, with
Roman jet workshops situated in York sending worked jet
ornaments and jewellery to all
parts of the Roman Empire. After
the Roman armies left in the 4th century AD, Britain
entered into the Dark Ages, and was for the next 500 years
under constant attack from
invading armies. Although the small scale use of jet continued throughout this troubled
period, it was not until the Vikings settled in the 9th century AD that jet once more came
to be more widely used for jewellery and small carvings.
invading Vikings had either left, or had settled and become assimilated into
Anglo-Saxon and Celtic cultures, jet was for the next thousand years used
mainly for ecclesiastical jewellery such
as crosses, rosaries, and rings. Then, in the
early 1800s, the use of jet for jewellery and ornaments began what
would prove to be a
dramatic resurgence in popularity which would last until the end of the 19th century.
As jet of
the finest quality can only be found near the historic fishing town of Whitby
situated on the
North Yorkshire coast, it is fitting that Whitby was at the
centre of that
most remarkable period in the history of
jet, the Victorian era.
Although as many as ten jet
workshops were operating in Whitby by 1815, it was not
until the mid-1800s that the
industry became truly well established, with demand increasing not least due to the
opening up of Whitby via
the railway combined with Victorians' love of seaside holiday
souvenirs. However, it was the Victorian vogue for
jet mourning jewellery which
contributed most significantly to the growth of the
Whitby jet industry at this time.
Victorian fashion was predominantly class-led, with Queen Victoria herself ultimately
setting the example.
Jet has been
associated with mourning in the Royal Court since 1830, but it was the
deaths of the Duke
Wellington and Prince Albert in 1852 and 1861 respectively
which really stimulated
wider public demand for jet mourning jewellery. The Whitby jet industry was at it's height
in 1873, at which time approximately 1,500 men were
employed in some 200 manufacturing
workshops. Raw jet was not only being avidly collected from local beaches,
but was being
commercially excavated at a number of inland locations in the North York Moors area, with
mines extending as far inland as Bilsdale and Osmotherly. However, in spite of efforts of
miners to procure ever
increasing amounts of raw jet, demand became so great in the 1870s
and 80s that some manufacturers resorted to
using inferior 'soft' jet sourced either locally from geological layers in
the cliffs other than the jet-rock proper itself,
or from France and Spain.
from 'soft' jet began to craze and crack soon after they were sold. In addition to such
of quality control, fashions in the latter part of the 19th
particularly the Art Nouveau 'naughty nineties - dictated the wearing of
pieces of jewellery.
"Black As Jet"
"Ah! Black as jet, but long ago
Indignity and lace,
The Ladies wore around their necks
A flash of ebon grace.
But oh! To-day Great Broughton mourns,
Still waves the merry corn,
The beer flows at Jet Miners' Inn,
But jet's no longer worn.
Still, fashions change, mayhap some day
Again the craft will thrive,
And Yorkshire jet will ring the earth,
Black, flashing and alive."