Gilwern Quarry, Powys

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On Sunday 3rd November, we re-visited Gilwern Quarry, Powys, to hunt for trilobites and other Ordovician goodies!

Gilwern quarry is privately-owned and is situated on the edge of the Brecon Beacons, in beautiful and isolated moorland. Gilwern is famous for its trilobites, which are generally very well preserved, and can be found in abundance. Gilwern Hill is made of Lower to Middle Ordovician volcaniclastic rock, which form part of the Builth Inlier. The site has rocks from the Llanvirn series (approximately 460 million years old) and exhibits the following beds:

·         Upper Didymographus murchisoni Shales

·         Pale flinty, tuffaceous beds

·         Main Rhyolitic tuffs, with Lower Didymographus murchisoni Shales

·         Rhyolitic tuffs and agglomerates

·         Upper Didymographus bifidus Beds

·         Lower Didymographus bifidus Beds

The site has been interpreted as a near-shore, shallow water environment, which due to the number and range of ages of Ogyginus found here, was identified as a breeding ground for the Ogyginus trilobite.

A small group of us were met by the landowner, Emma, at the on-site shepherd’s hut. Emma gave us her amazing warm welcome, with hot teas and coffees at the ready! For those of us who had travelled far, this was most welcome!

We were very lucky with the weather, as the previous week had seen torrential downpours, with part of the quarry under several feet of water. Despite this, we found a great selection of whole and partial Ogyginus and Bettonolithus trilobites.

The beautiful view from the shepherd’s hut
Large Ogyginus trilobite!

We would like to thank all for attending – we hope you had a fantastic day! A special thank you goes to Emma for her fabulous hospitality!

Access to the quarry and rental of the self-catering shepherd’s hut can be requested via

For further information on Gilwern fossils, please refer to

Leader selfie! (Sam, Terry and Mike)

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