Valentia Slate Quarry – purple stone

Overview

Valentia slate is purple, takes a high polish, and ended up in the Palace of Westminster and the Paris Opera House. The quarry that produced it sits on the western edge of Knightstown, the main village on Valentia Island, County Kerry, and is the only slate quarry still working in Ireland as well as the most westerly in Europe. You cannot go into the working face on your own, so the public view is from a small Marian grotto perched 100 ft above the entrance, with statues of Our Lady and Bernadette installed in 1954. Note that the grotto has closed intermittently for rock-fall works since 2023, so check before you set out.

History

Maurice Fitzgerald, the 18th Knight of Kerry, founded the quarry in 1816 to supply roofing and flooring slates. Early extraction was at Dohilla, where two underground chambers were opened; the deeper one, the Grotto Chamber, runs about 150 m into the hillside and rises 20 m high. Slate was squared on site, then taken to a yard in Knightstown where slabs roughly 2 m long and 25 mm thick were prepared for export.

By the mid-19th century the slate was leaving from a purpose-built pier, designed by Alexander Nimmo in 1825, for projects including:

• The Palace of Westminster, notably the encaustic floor tiles in the corridors.
• Westminster Abbey and St Paul’s Cathedral.
• Several London Underground stations: Waterloo, Charing Cross, Liverpool Street and Black Friars.
• The Paris Opera House.
• Queen Victoria’s summer residence, Osborne House, where a white-enamelled Valentia slate billiard table still stands.

At its peak the quarry employed between 200 and 500 workers. A rock-fall in 1911 stopped production, and the site lay dormant until 1999, when three local entrepreneurs revived it as Valentia Slate Ltd. It has run ever since.

The grotto dates to the Marian year of 1954. A hand-built ladder, still visible, was used to hoist the statues of Our Lady and Bernadette into the cave, turning the cave mouth into a place of pilgrimage and occasional mass.

Geology and heritage

Valentia slate is a penetratively cleaved, fine-grained siltstone of the Valentia Slate Formation, part of the Iveragh Group. It dates to the Middle Devonian (Givetian) and was laid down on an alluvial flood-plain about 385 million years ago. The purple colour is consistent through the stone and develops a patina with use.

In 2024 the quarry was designated an IUGS Geoheritage Stone for its scientific importance and its long contribution to architecture. The IUGS entry singles out a ‘chimney’ feature, a vertical column-like exposure of the slate that geologists like to photograph.

What it was used for

• Roofing and flooring slates for 19th-century UK industrial units, schools and prisons.
• Paving stones and garden furniture cut from off-cuts.
• Cisterns for water or spirits.
• Billiard tables, some enamelled in a patented process by George Magus, a former lessee; the Osborne House table is one.
• Modern countertops, fire surrounds, floor tiles, memorials and signage, still made on site.

Under geologist Dr Aidan Forde, Valentia Slate Ltd works to a zero-waste philosophy, recycling all off-cuts into garden furniture or decorative pieces. Recent commissions show how far the stone travels: 32 notched standing stones and paving for the refurbished Béal na Bláth monument in 2022, marking the centenary of Michael Collins’s death, and a €9,500 slate chair by designer Edwyn James Hickey for the Art Evolve exhibition at the RDS in 2025.

What to see and do

• Grotto viewpoint – the short, well-marked path from the quarry barrier to the grotto, where the ladder remnants and the two statues give a sense of the 1950s effort.
• Quarry walls – the interior is off-limits, but the sheer dark rock faces read well against the surrounding green from the grotto area.
• Guided tours – in summer the quarry runs hourly tours from 10am to 4pm (April–October), into the working face, with the diamond-studded cutting rope and a go at shaping a roofing slate.
• Miner’s View – a viewpoint on the Geokaun Mountain road, signposted locally, for a wider shot of the entrance and the coastline.
• On-site shop – handcrafted slate, from small countertop slabs to garden benches.

The quarry is a regular stop on the Ring of Kerry walking itinerary, which pairs the geology with the coast.

Safety and access

A run of rock-fall incidents in late 2023 and early 2024 closed the ground-level grotto area for safety while stabilisation works were carried out. The statues and altar stayed intact, but the pathway was cordoned off. Dr Aidan Forde continues to work with the Diocese of Kerry on an entrance that keeps pilgrims safe alongside the working quarry. Check the latest access status on the quarry’s website before you go, as the grotto may close again during works.

Practical information

Getting to the quarry

By road, from the Ring of Kerry follow signs to Portmagee, cross the bridge and continue north on the R564 to Knightstown. Past the Royal Hotel, turn left onto School Road and follow the quarry signs for about 2 km. By ferry, the Valentia Car Ferry runs between Reenard Point near Cahersiveen and Knightstown from April to mid-October; the crossing takes about five minutes, then follow the same road directions.

The grotto itself is free. Mass is held occasionally and announced locally. It is a quiet spot with a view over the Atlantic.

Nearby attractions

• Geokaun Mountain – views of the Skellig Islands and the Atlantic.
• Tetrapod Footprints – a 385-million-year-old fossil trackway near the quarry, among the oldest land-animal footprints known.
• Knightstown Coffee – a café in an 1888 building, good for a quick stop.
• Valentia Heritage Centre – on the island’s trans-Atlantic cable and local history.