The Blorenge sits on the extreme eastern rim of the South Wales Coalfield, hemmed between the Usk Valley to the north and the Blaenavon industrial corridor to the south. Its broad, anvil-shaped summit consists of carboniferous limestone and hard quartz conglomerate, capped with a thick mantle of Old Red Sandstone. This geology created the stark drop-offs that plunge northeast toward Abergavenny, contrasting sharply with the long, peat-lined gentler slopes falling away to the south.
Centuries of iron smelting, coal mining, and limestone quarrying altered the lower slopes. The mountain does not just form a backdrop for hikers; it forms part of the Blaenavon Industrial Landscape, a designated UNESCO World Heritage site. Rail networks and tramroads once ferried pig iron down the mountainside to the Brecknock and Abergavenny Canal. Today, those same rail beds provide direct footpaths into the high moorlands, forming part of the regional Iron Mountain Trail network.
