This site comprises two adits driven into opposing banks of a small river which bisects the workings. The adit on the far bank is flooded to a depth of approximately 0.9 m, with an airspace of around 0.6 m above water level. The second adit lies a short distance around the bend on the near side of the stream.

A short distance inside the accessible adit, a substantial winze is encountered. Immediately to the right, a side passage leads to a small stope containing a further short winze; this area provides the only clearly visible evidence of vein extraction. Beyond the principal winze, the adit continues and branches in several directions, apparently exploratory in nature and suggestive of a search for a workable vein.

Despite limited surface indications, the underground workings are more extensive than might initially be supposed. The mine is reported to have been surveyed by Harold Morris, and numerous pill bottles suspended on strings were observed underground, presumably serving as survey markers.

See forum discussion for details of 2026 visit on which above description is based.

Referenced in Diwydiannau Coll by Bob Owen ‘Croesor’ [1885-1962]:

Tynddol. Here there are remains of quite a large copper mine with a long level, and the spoil tips show that there was extensive digging here. On the tips are the ruins of the old huts where they used to work the copper. No one remembers this place being mined. [Translated by B. Anne Richards 1953-1974]

User Graigwen (in the UKCaving link) cautions:

When Bob Owen says “…quite a large copper mine…” he means by contrast to small trials. Bob Owen collected his information before 1943. I went to this site in 1971 and don’t remember any remains of huts…but it was a long time ago.