Tan-Y-Garn (Under the Mountain), South Wales
Tan-y-Garn is more remote than the other sites, surrounded by trees, tucked into the side of a high valley in South West Wales. The deep orange ochre that forms here begins as rain water percolating through the rocks, finding routes through the cracks and fissures of the former mine workings absorbing minerals on the way. Eventually the mineral rich water leaches out from the mine adit at the base of the mountain, oxidising and gaining its colour.
The water treatment process uses limestone and mushroom compost to reduce the acidity of the mine water. The limestone raises the pH which helps iron oxidation and the mushroom compost supports bacterial processes causing anaerobic conditions that prevent the limestone becoming clogged.
Tan-y-Garn it is a deep red brown. When suspended in water different colours are visible as the pigment particle sizes vary. It moves between bright orange through to deep purple with a blood like brownish red that dominates the final colour.
The mine here was worked until the early 1990’s, supplying fuel for the Port Talbot Steel works.
