Dinorwic quarry

Dinorwic quarry, showing major inclines, mills, levels, and tramways, and the Padarn Railway and Dinorwic Railway

The slate vein at Dinorwic is nearly vertical and lies at or near the surface of the mountain, allowing it to be worked in a series of stepped galleries . This is however not quite how the quarry developed.

The first quarrying was spread across several sites: Adelaide, Allt Ddu, Braich, Bryn Glas, Bryn Llys, Chwarel Fawr, Ellis, Garrett, Harriet, Matilda, Morgan's, Raven Rock, Sofia, Turner, Victoria, and Wellington.[3] This was a situation that lasted for many years, certainly until the mid-1830s.

The 1824 railway brought transport problems. Produce from the upper quarries was not a problem, but Wellington, Ellis, Turner, Harriet, and Victoria quarries were all below the level of the railway. This was a problem solved in the 1840s when the lake level railway was built, and the quarry as we know it began to take shape.

Adelaide quarry became a part of Allt Ddu, and Chwarel Fawr and Chwarel Goch became linked to it too. In the 'Great New Quarry', Raven Rock and Garret Quarries became one massive quarry, operating as an open hillside gallery quarry, with the lowest two levels being accessed by tunnels. Harriet, Morgans, and Sofia quarry are all still identifiable as separate pits today, whilst Braich quarry became a large working of three contiguous smaller pits. Below this, The galleries of Victoria and Wellington were joined along the hillside and continued downwards in two separate main workings: Wellington and Hafod Owen. Each was eventually to contain several small sinks too, some below lake level. The current form of the quarry is little different from that of the time of the Great War, save for enlarging of the actual quarry faces and deepening of the sinks. Certainly, all the main inclines were in place, very little was altered until closure.[4]

The nearby Marchlyn quarry was opened in the 1930s to provide access to the main slate vein higher up the mountain.

The quarry closed in July 1969, the result of industrial decline and difficult slate removal.[2] During the 1950s/60s extraction had become difficult, because after 170 years of extraction many of the unsystematically dumped tips were beginning to slide into some of the major pit workings, and after an enormous fall in the Garret area of the quarry in 1966, production had ceased almost permanently. It was however decided that some final work could be done by clearing some of the waste from the Garret fall. This involved making an access road for more modern quarry vehicles across some of the terraces, to the rockfall. This amount of slate won by this method was small and all production stopped by 1969.

At the Receiver's instruction a public auction was arranged, intended to pay off some of the quarry's debts. The auctions were held on 12 and 13 December 1969. The auctioneer's national advertisement (in The Guardian 29 November 1969), the event was described as "An auction sale of machine tools and stocks, four Hunslet locos, and engine and boat fittings". The locomotives referred to, lots 613–616, were "Dolbadarn", "Red Damsel", "Wild Aster" and "Irish Mail". Before the bidding started, it was announced that Gwynedd County Council had placed a Preservation Order on the Gilfach Ddu workshops, and many items within it.

The first use of railways at the quarry came around 1800 when the first internal tramways were in use. These first lines were worked using horse- and hand- power. For the next seventy years, the tramway system grew until it reached the point where more powerful traction was required. The first steam locomotives used were small vertical boiler locos supplied by De Winton's of Caernarfon. In 1870 the first locomotive supplied by the Hunslet Engine Company arrived at the quarry, and the majority of the locomotives that worked at Dinorwic were eventually supplied by Hunslet.[2]

Between 1935 and 1949 the Quarry acquired 22 light internal combustion rail tractors for use on the levels. Half of these were new, the other half second-hand. Their survival rate did not match those of the steam locomotives, and when the quarry closed in 1969 only three still survived.

Although a nominal two-foot gauge, the actual gauge between the rails at Dinorwic was 1 ft 10+3⁄4 in (578 mm)[5] in common with its neighbour Penrhyn, but fractionally narrower than the public lines of the Ffestiniog Railway or North Wales Narrow Gauge Railway which were 1 ft 11+1⁄2 in (597 mm).

Early steam locomotives were used by the quarry, and built by De Winton & Co. But from 1870 the quarry acquired most of its locomotives new from the Hunslet Engine Company of Leeds. These were purpose-built, initially using a series of Hunslet general/unclassified designs, but after 1886 these fell into one of three classes:

• Alice
• Port: larger and designed primarily to work at Port Dinorwic, although Michael never did.
• Tram or Mills: worked on marshaling duties on the Padarn–Peris Tram Line, which linked the quarry mills to the Padarn Railway for transportation to Port Dinorwic.

Orig. name / number	Later name	Image	Builder	Year acquired	Year sold	Notes
Wellington			De Winton	c1870	1898
Harriet			De Winton	1874	pre 1895
Peris			De Winton	1875	pre 1895
Victoria			De Winton	1876	pre 1895
Padarn			De Winton	c1898	?
Dinorwic	Charlie		Hunslet	1870	by 1919
George	Minstrel Park		Hunslet	1877	by 1919
Louisa			Hunslet	1877	by 1989
Sybil			W. G. Bagnall	1906	?	Restoration project taking place at the West Lancashire Light Railway
No.70			Barclay & Sons	1931	1962
Elidir			Avonside Engine	1933	1966
Velinheli			Hunslet	1886	1965	Alice class Now preserved at the Launceston Steam Railway. Currently on loan to the Ffestiniog Railway.[6]
Alice	King of the Scarlets		Hunslet	1889	1965	Alice class Preserved at the Statfold Barn Railway
Enid	Red Damsel later Elidir		Hunslet	1889	1969	Alice class
No.1	Rough Pup		Hunslet	1891	1968	Alice class Preserved at the NGM
No.2	Cloister		Hunslet	1892	1962	Alice class preserved at the Statfold Barn Railway
The First	Bernstein		Hunslet	1892	1967	Alice class
The Second	Covertcoat		Hunslet	1898	1964	Alice class
Wellington	George B.		Hunslet	1898	1965	Alice class Now at the Bala Lake Railway[7]
No.3	Holy War		Hunslet	1902	1968	Alice class
No.4	Alice		Hunslet	1902	1972	Alice class
No.5	Maid Marian (briefly Covertcoat)		Hunslet	1903	1966	Alice class
No.6	Irish Mail		Hunslet	1903	1969	Alice class preserved at West Lancashire Light Railway
No.7	Wild Aster now Thomas Bach		Hunslet	1904	1969	Alice class Now running on the Llanberis Lake Railway
No.1	Lady Joan		Hunslet	1922	1967	Port class
No.2	Dolbadarn		Hunslet	1922	1969	Port class
Michael			Hunslet	1932	1965	Port class Preserved at the Statford Barn Railway
Vaenol	Jerry M		Hunslet	1895	1967	Tram/Mills class Now at the Hollycombe Steam Collection
Port Dinorwic	Cackler		Hunslet	1898	1966	Tram/Mills class

Welsh Slate Museum located in Gilfach Ddu

Following closure, the quarry's workshop at Gilfach Ddu was acquired by the then Caernarfonshire County Council, who now lease the building to the National Museum and Galleries of Wales. It now houses the National Slate Museum. Equipment from the internal quarry railway was used to build the Llanberis Lake Railway over part of the trackbed of the Padarn Railway. The quarry has been partly used by the Dinorwig power station, a pumped storage hydroelectric scheme. Many of the Hunslet locomotives have been preserved on several of Britain's narrow gauge heritage railways. More recently, new build versions of the class have been built by the Exmoor Steam Railway, and by a new Hunslet company at the Statfold Barn Railway.

In 1987, part of the film Willow was shot in the Dinorwic quarry, on the lower terraces next to the pumped-storage scheme. Scenes from the 1994 film Street Fighter were filmed on the south side of "Watford Gap" near the Matilda hole.[8] Clash of the Titans was filmed in the quarry in 2009.[9]

The Dinorwic quarry has also become a major British rock climbing venue, particularly the sections of Twll Mawr (meaning "big hole"), Vivian quarry, Rainbow Slab, and Australia. Famous British rock climbers such as Johnny Dawes have created well-known extreme test-pieces such as the traditional climbing route The Quarryman (E8 7a) in the Twll Mawr section, and the sport climbing route The Very Big & the Very Small 8b+ (5.14a) in the Rainbow Slab section, of the Dinorwic quarry.[10] The most famous route is Stevie Haston's Comes the Dervish (E3 5c) in the Vivian quarry section,[11] and the hardest route is currently James McHaffie's sport climbing route, The Meltdown at 9a (5.14d) (previously bolted and attempted by Dawes and Jerry Moffatt), also in the Twll Mawr section.[10]

The Vivian quarry section is also used for diving, with good visibility and depths ranging from 6–18 metres (20–59 ft), a platform at 6 metres (20 ft), plus flooded buildings, boats, a van and a gnome garden.

• "Penmorfa article on Dinorwic".
• Narrow Gauge Railways in North Caernarvonshire: Volume 3. Boyd, James I.C. (1986). The Oakwood Press; ISBN 0-85361-328-1