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Miners
Tramway
Boarding
a train in a corner of the original slate slabbing mill of 1852, visitors
now ride into an 1846 tunnel, hauled by battery-electric locomotive.
Entering through the side of the mountain this journey into the early
Victorian past remains on the level, and traverses some spectacular
caverns.
To find
out more, click here. |
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Deep
Mine
Visitors
descend on Britain's steepest passenger railway, with a gradient of
1:1.8, to make the Deep Mine tour. They travel in a specially made 24-seat
car, on a track with a gauge of 3ft (0.914m).
To find
out more, click here. |
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What
is Slate?
Geologists
are reluctant to describe their time scale in insignificant calendar
years, but a consensus of international research tells us the Blaenau
Ffestiniog beds of superb Ordovician blue-grey slate were heaved out
of the sea about 500 million years ago. They are about 100 million years
younger than the purple slate beds of the Caernarfon area.
That,
however, is only a tiny fraction of a story that defies calculation,
for slate is stone for the second time round! Countless hundreds of
millions of years of wind, rain and chemical reaction eroded the world's
first rocks, washing the resultant minute particles into the sea. There
the tiny particles built up into layers of clay several hundred feet
thick. Later volcanic reaction created folds in the earth's crust, heaving
new mountains out of the seabed, with the accompanying compression and
movement making all the particles lie in the same direction. Heat from
the intrusion of volcanic gasses and lavas caused some of the original
mineral particles to make new chemical combinations, especially minute
flat ribbon-like particles of mica, which account for about 55% of the
natural bulk of Llechwedd slate.
Mica
crystals measure a virtually invisible 1/2000th of an inch in length
and 1/6000th in thickness. Their presence gives Llechwedd slate most
of its universally prized properties, notably the fineness to which
it can be split. At the London Exhibition of 1862 John W. Greaves, founder
of Llechwedd, won a medal with slates 10ft long and 1ft wide, but only
1/16th of an inch thick. At a competition in 1872 everyone marvelled
when a Llechwedd quarryman split a block 2.5 inches thick into 45 layers.
Today it is commonplace for splitters to produce about 35 sheets per
inch when making delicate slate ornaments, such as fans using a chisel
adapted from a table knife and blocks from the exceptionally fine quality
Old Vein.
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