Haematite at Limeslade Bay (East)

A geological fault runs right through the limestone of Mumbles Hill near Swansea. Within this north-south fault, calcite crystals formed. Iron minerals from a former covering of Triassic strata, percolated down and filled in the spaces between the calcite crystals in the fault. The iron minerals, in the form of haematite (sometimes called hematite) also replaced the calcite crystals in some places.

This source of iron was an important discovery for the Romans who began to mine it nearly two thousand years ago. Mining continued until the late 19th century. The deposits of calcite and haematite varied from two to four metres wide but mining activities widened the seam out. The damage left by the mining can still be seen today as ‘The Cut’ which crosses the hillside of the Mumbles Nature Reserve – although now in-filled, the scar is still evident.

Down on the seashore at Limeslade Bay (part of the south shore of the Gower Peninsula) the eroded southern-most extremity of the fault with its remnants of calcite and haematite are visible. The opening to The Cut is sealed up with a wall where the road passes over-head. A further walled-up stonework barrier to the adit can be seen on the landward side of the road behind a kiosk.

In the outcropping Carboniferous Limestone on Limeslade beach, the bright white crystalline calcite and blood-red haematite make quite a display, often looking like joints of meat. Occasionally, the iron ore appears in a dark red, purple, or nearly black form. Vivid red cobble-sized beach stones of haematite strike a noticeable contrast amongst the other more numerous grey limestone pebbles, or stand out against the green seaweed in rock pools.

REFERENCES

Barclay, W. J. (2011) Geology of the Swansea District: a brief explanation of the geological map Sheet 247 Swansea,  British Geological Survey, Natural Environment Research Council,  ISBN 978-085272581-8, p 30.

Bridges, E. M. (1997) Classic Landforms of the Gower Coast, Series Eds. Rodney Castledean and Christopher Green, The Geographical Association, The British Geomorphological Research Group, ISBN 1-899085-50-5, p 16.

George, G.T. (2008) The Geology of South Wales: A Field Guide, published by gareth@geoserve.co.uk, ISBN 978-0-9559371-0-1,  pp 86 – 87.

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