Located on a spur projecting from the north side of the Ystwyth valley is a round cairn. It consists of a low grassy mound through which project, or in which are embedded, large stones, mostly slabs. It measures about 8.5m in diameter and 0.4m high. Just north of centre is a rectangular cut measuring 1.5m by 0.75m and 0.3m deep. The north edge of the mound has been damaged by a mine leat running north-west to south-east, and another passes close by on the south side of the cairn.
The cairn is surrounded by structures related to mining which might explain its depleted state. However, it remains possible that it is an eroded outcrop exposure. But if genuine, it is one of very few monuments broadly contemporary with nearby Early Bronze Age mining activity.
David Leighton, RCAHMW, 12 July 2013

Recent investigations have shown that the cairn lies precisely on the outcrop of the Comet Lode. Excavations revealed a circle of stone slabs up to 1.5m long forming a circle about 9m in diameter which enclosed a shallow stone cairn built around a slightly off-centre rock outcrop, with a `cove? structure of four stones at centre, and two-three intercutting shallow pits cut through the cairn. These pits contained spreads of charcoal but in one was found two halves of a polished perforated stone macehead of Late Neolithic date. As no link was found between the cairn and local mining it is therefore likely that the cairn predates the Early Bronze Age workings.
On the south-east side of the cairn a thin spill of cairn material overlay a black peaty buried soil containing a scatter of broken-up quartz vein, some with traces of galena. The soil provided a C14 date of 265-420 Cal AD indicating post-cairn activity, perhaps Roman prospecting.

Additional source:
Timberlake, S. 2017. `Archaeological excavations at Cwmystwyth mine - Pant Morcell [SN80627502] `, Welsh Mines Society Newsletter 76 (Spring 2017), 28-9.

David Leighton, RCAHMW 11 August 2017