UK Grid Reference: SH681463
Latitude: 52°59'50"N
Longitude: 3°57'56"W
Old slate quarry workings that linked underground to Gloddfa Ganol (Oakley) Quarry; the slates are cut by various basic dykes and by tuff turbidite bands (known to the miners as "cherts") that run through the slate.
The minerals at Cwmorthin Quarry largely occur in small cavities in alpine-type veins within the "cherts". These contain quartz, anatase, synchysite and xenotime with minor albite, apatite, rutile, brookite, galena and pyrite also occuring. Elsewhere, pyrite occurs in direct contact with the slate and pyrrhottite has been found in small cavities in quartz.
Minerals at Cwmorthin Quarry are generally rare, and whilst quartz can occur to several cm, other minerals are generally much smaller, or microscopic in nature.
Mineral List
11 entries listed. 10 valid minerals.
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