There are various odd minor mineral occurrences in the Penmaenmawr area - wasn't there a level for asbestos on the north-facing side? Foster-Smith notes nothing north of Trecastell but as his desk top reconnaissance seems to have been based on 1:25,000 OS maps, he inevitably missed some outlying trials.
I can't see anything marked on six inch maps on the NLS website but noticed a level that appeared for the first time on the 1911 edition, located about 100m east of Castell Caer Lleion, the hillfort on the summit of Conwy Mountain, which appears to have lain at the east end of a tramway and incline system. It lies on the north side of the mountain, only perhaps 75ft below the summit ridge to judge from the contours on the 1948 edition six inch map. Does anyone know anything about it?