Description: Siegenite Gelli Colliery, Gelli, Rhonnda-Cynon-Taff, Wales, UK Platy siegenite crystal 6mm across, with smaller octahedral siegenite crystals scattered around it. This is huge for the south Wales Coalfield and, to my knowledge, much the largest found in the UK. Identification confirmed at the National Museum of Wales. Collected August 1988.

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