Marchlyn Mawr, Llanberis, Gwynedd (Caernarvonshire), Wales, UK
The natural lake Marchlyn Mawr has been dammed to form the upper reservoir of the Dinorwig Pumped Storage Scheme, the largest pumped storage hydroelectric scheme in Europe at the time of its construction in 1984 (see also Dinorwig Quarry, the site of the lower reservoir).
UK Grid Reference: SH616619
Fibrous, radiating aggregates of thomsonite occur here infilling vesicles to 20 mm in diameter in the Marchlyn Dyke; an olivine dolerite of Palaeogene age.
Williams, D., 1930. The geology of the country between Nant Peris and Nant Ffrancon (Snowdonia). Quarterly Journal of the Geological Society of London, 86, 191-232.
Williams, D., 1924. On two olivine-dolerite dykes in Snowdonia. Proceedings of the Liverpool Geological Society, 14, 38-47.
1 entry listed. 1 valid mineral.
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New Locality Added: Alais meteorite, Gard, Languedoc-Roussillon, FranceFrom Lon Clay Hill, 9th Dec 2013 14:09:10