Trefil Quarry

Situated just outside Trefil, the highest village in Wales, this is a former limestone quarry, which once supplied the Sirhowy Ironworks and contains the remains of a Carboniferous coral reef.


♦ From the A465 Heads of the Valleys Road, you will see an exit signposted for Tredegar and Trefil. From the roundabout, take the road north towards Trefil.
♦ If travelling up the valley from Tredegar, take the A4048 north and you’ll arrive at the same roundabout. Head north towards Trefil.
♦ When you reach Trefil, follow the same road until you come to a cattle grid and barrier. The quarry road is closed to traffic, so park on the grass verge at the right-hand side of the road just before the barrier.
♦ Walk north along the quarry road, past the barn on the right, then follow the rocky track off to the right until you reach a track leading to the entrance of the working quarry on the right.
♦ Do not enter the working quarry. Instead, cross over the main track and walk through the gap between small mounds in front of you. This will take you to the old quarry.
♦ SO 11746 13944


FIND FREQUENCY: ♦♦♦ – Most areas of the quarry contain fossils in the scree, but it may take a while to get your eye in as many of them are the same colour as the bedrock.
CHILDREN: ♦♦♦ – The quarry floor is quite uneven apart from the old tram road through the middle, with many large boulders and scree slopes. Older children should be fully supervised to ensure their safety. The location is not suitable for very young children.
ACCESS: ♦♦♦ – Parking is free but limited, being on the side of the road at SO 11975 12932, just before the barrier. There is a walk of about a kilometre from the parking spot to the quarry, but any reasonably fit person should find it straightforward enough.
TYPE: – Fossils can be found in the scree slopes and piles of quarrying waste on the quarry floor.


Trefil Quarry was opened to supply the nearby Sirhowy Ironworks with limestone in the eighteenth century. The old quarry is now abandoned, and access is open to all. However, quarrying continues at the nearby modern working quarry, to which access is restricted. Fossils can be found in all areas of the quarry, but you should focus your attention on the dark grey fossiliferous limestone. Avoid the white-coloured sandstone and conglomerate blocks, since these contain very few fossils.

Scree slopes and patches of loose rocks occur all around the quarry and fossils can be found in most of them. If you find a patch that contains few fossils, move on to another nearby patch and you will probably have more success.

In the northern part of the quarry, there is a layer that can be seen going right around the quarry that contains many corals in situ. Do not attempt to remove these but leave them for others to see. Plentiful examples of these corals can be found in the fallen blocks.

Various species of coral, including Syringopora, Siphonodendron and Siphonophyllia, can be found here. Productid and spiriferid brachiopods are also common, along with gastropods. Less common but also present are several species of bivalve, while trilobites are rare but can be found.


The quarry faces are entirely Carboniferous, comprised mainly of the grey-coloured Dowlais Limestone Formation, which is of Holkerian age (343 to 337 million years old). These rocks were formed in a coral reef in a shallow tropical sea.
You will also find white sandstone and conglomerate boulders from the younger Twrch Sandstone Formation (from the Pendleian to Yeadonian, 329-319 million years old), but these tend to contain very few fossils.


Common sense when collecting at all locations should always be used Please keep away from the steep sides of the quarry and falls still occur. There are a lot of large boulders on the quarry floor which are sometimes hidden in the vegetation, so care should be taken.


Several bags and either bubble wrap or newspaper to wrap your finds in are the main equipment needed at this location. However, a geological hammer and safety glasses are essential for breaking up larger blocks of limestone, as the rock is very hard.


The old quarry is on common land, so there are no known access restrictions. However, motor vehicles are not permitted on the quarry road (bridleway) beyond the barrier.

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