Old jasper quarry, Mynydd Carreg, near Aberdaron

Old jasper quarry, Mynydd Carreg, near Aberdaron

Photo of block of Aberdaron jasper in PwllheliJasper, regarded as a semi-precious stone, was once quarried at Mynydd Carreg, near Porth Oer. The site is visible across the fields as you look south-west from Porth Oer car park.

Jasper is a metamorphic rock formed in the late Precambrian Neoproterozoic era, between 1,000 million and 541 million years ago.

In 1901 veins of Jasper up to 37 metres (40 yards) wide were discovered at the base of Mynydd Carreg. Jasper also outcrops in the sea cliffs nearby.

The discovery was made by a group of “mining gentlemen”, who included mining engineer Captain John Trevethan from Rhyl. He reported that the jasper was mostly cherry red, and some was pink, buff or almost white.

Stone experts in Birmingham were impressed with samples and requested further “chippings”. They were amazed when told that tons, not ounces, were available! A one-ton block had already been sent to London. In 1905 a block weighing 11 tons was dispatched to London.

Photo of Aberdaron jasper on building in Piccadilly, London

Jasper was quarried here on a small scale from 1904 until 1907, when a larger operation began. The stone must have been expensive to deliver, as it had to be hauled c.32km (c.20 miles) by traction engine to the railhead at Pwllheli! A bridge c.1km away collapsed under the weight of a traction engine hauling jasper. The upper photo, courtesy of Rhiw.com, shows a block of jasper in the centre of Pwllheli, near the railway station (with the spire of Capel Tabernacl in the distance).

Jasper from Mynydd Carreg was described as being over twice as strong as granite and able to withstand weathering in any climate. It still clads the ground-floor exterior walls of the Norwich Union building on the corner of St James Street and Piccadilly in London. The building opened in 1908 and is pictured here courtesy of Dr Ruth Siddall. The quarry virtually ceased to operate soon after but records show that it was employing 18 people again in 1914, as it had in 1908.

With thanks to Mike Statham and Dr Ruth Siddall, of the Welsh Stone Forum

Postcode: LL53 8LH    View Location Map

Footnotes: More about the jasper

Mynydd Carreg jasper has been described as a dolomitic marble (dolomite is calcium magnesium carbonate), though the rock composition is complex and probably contains a significant amount of siliceous material. The colouring varies, red being due to the presence of iron in the form of haematite, whilst the pink colouration is due to the manganese mineral rhodochrosite.

Rhiw.com website - more history and photos of Llŷn Peninsula