Slate Industry of North and Mid Wales
Nantlle and Dorothea Slate Quarry
A view of part
Nantlle with Craig Cwm Silyn in the distance.
the North West corner of Wales lies a long belt of Cambrian
about 500 million years ago. This stretches from the
valley in the East to the Nantlle valley in the West.
belt were situated some of the largest and most productive
in the world. In the east the slate was won by open
the gallery method, while at the west end, the slate beds were
the floor of the valley. It was the depth of the slate
valley floor which influenced the quarrying techniques of
The only way to obtain the rock was by digging down and
pits. These can be found in many locations in the
Some of the difficulties of pit working included the need to
pump out any
water entering the workings and the need to haul out waste as
well as good
rock. Both of these imperatives increased costs, added
to which was
the Nantlle area's greater distance from the markets.
was always at a disadvantage compared to the more easily won
rock at Penrhyn
and Dinorwic further east and was always the first to suffer
from any downturn
Image produced from the Ordnance Survey
difficulties were faced by the Nantlle industry. There
were a large
number of very small quarries, a situation brought about by
These small quarries had little capital to invest and no way
Although there were amalgamations and takeovers which created
like Dorothea, the tradition of the small quarry survived and
can be seen
today in the long line of small workings along the south side
of the valley.
Another major problem was disposal of waste rock. After
and trouble of bringing it up to surface level, it then had to
up again onto the raised waste tips, so typical of the
of course meant that any winnable slate under the waste tips
to remain there. If history had been different and the
had been operated as a single undertaking, then the prospects
slate could have been transformed.
A view of
pre 1940 looking east. The wires and towers
are for the aerial ropeways or "Blondins".
The oldest quarry
in the Nantlle district was Cilgwyn quarry, this is situated
to the north
of Dorothea on the hillside and is now a landfill
site. It is thought
to have been first worked in the fourteenth century and it
that some of Edward the 1st's Welsh castles were roofed with
itself opened in 1820 and remained in production until
The land the quarry stands on was owned by a Richard Garnons
but the main driving force for quarrying in the valley was a
- William Turner (1776 -1857). The original name
for the quarry
was Cloddfa Turner but it was renamed Dorothea after
The workings grew out of a series of smaller workings with
names such as
Hen Dwll, Twll Bach, Twll y Weirglodd, Twll Coch and Twll
the years these pits were deepened and amalgamated into the
pit seen today. Turner gave up his interest in the
quarry in 1848
and following a brief period of closure it was acquired by a
Hughes Williams was from Llangernyw near Denbigh. He married
into the Rev
John Jones of Talysarn's family & bought shares in
set up by Jones & local Nantlle quarrymen (though half
the money was
raised outside the area). Williams gradually
bought out most
of the others by the 1860s, and his family continued in
Remains of a
once used to haul slate out of the Dorothea quarry pit.
1828 the Nantlle Railway opened giving the quarries of the
valley a route
to the sea. The horse powered railway was of 3' 6"
and ran originally to Caernarfon. From 1872 the tramway
as far as Talysarn where connection was made with the national
The Nantlle Railway continued in use, as a part of British
1963 and remained horse worked until a couple of years before
The final two horses in use were "Prince" and
After the horses were retired a tractor was used for the
of traffic. Over its lifetime the route of the railway
many times as the quarries expanded. Much of its route
today as far as the easterly terminus at Penyrorsedd
Quarry used the Nantlle Railway to dispatch slate from 1829
There are two
large structures, known as pyramids, at Dorothea, they
served as bases
for the chain inclines and allowed the waste rock to be
By the 1840's production
at Dorothea had built up to about 5,000 tonnes per annum and
over 17,000 tonnes by the 1870's. The future looked
good for Dorothea
but serious flooding problems then befell the quarry.
In 1884 several
men were drowned when the pit was engulfed. In 1895
the Afon Llyfni
which flowed through the valley was realigned and deepened
to flow to the
south of the slate workings. This cured the flooding
some extent but as the workings deepened, the need to
out water became a constant drain on the quarry's
profits. In 1904
the decision was taken to install a Cornish Beam Engine on
site to replace
the waterwheels. The following
contains more details of the beam engine and engine house.
under one of the pyramids and once lead onto the Nantlle
the quarries of the valley continued to grow it led to the
removal of the
village of Talysarn which was relocated to the west.
Some of the
old village buildings remained in use by the quarries and
their ruins can
still be seen today. This was followed in 1927 by the
of the main road to the south of the valley. The route
of the old
road can still be followed.
lift the slate out of the pit, wire inclines were installed
in the 1840's.
There were ultimately eight of these and they were
complimented after 1900
by aerial ropeways or Blondins. At first steam
powered, the Blondins
were electrically worked from 1959. They remained in
use until 1965
when a road was built to the bottom of the pit. The
last of the wire
inclines went out of use in 1957. Other powered
used at the quarry to lift the waste rock up to the elevated
ropeways or "Blondins"
were used to raise the slate from the pits. These five
disused examples were
photographed at Penyrorsedd quarry in 1992. Today only
one is left
was an extensive rail network on site at ground level and on
tips. The track gauge of the internal quarry railways
was 2' (60cm)
as opposed to the "main line" gauge of the Nantlle Railway of
3' 6" (105cm).
There are records of 5 steam and 4 petrol driven locos being
used at various
times and horses were also used. Use of the 2'
rail network had ceased by 1968.
closure came about due to the national decline in the
industry, the slate
industry had reached a peak in the 1890's but from then on
it was a story
of contraction. Dorothea was no exception as tonnages
manning was cut - a cycle of decline set in. Other
in Dyffryn Nantlle also closed - Pen y Bryn in 1950 and
Cilgwyn (now a
landfill site) in 1956. Today the only significant
quarry still in
production in the valley is Penyrorsedd, now owned by the
Welsh Slate group,
and busily exploiting a newly found seam of green rock.
quarry pool in
the foreground with the Cilgwyn quarry tips behind.
Dorothea is a popular although unofficial diving centre and
have been quite a number of divers who have lost their lives
There have been numerous changes of ownership of Dorothea over
each successive owner promising investment and regeneration
only to be
replaced by yet another optimist with yet more plans. A
Dyffryn Nantlle is highly recommended before development
changes the character
of this unique area for ever.
Cornish beam engine at Dorothea Quarry
"Aspects of the Slate Industry"