Opencast Working

Any mine working carried out as an open excavation from the surface downward, rather than underground — a broad excavation or trench following a vein or bed, distinct from a shaft or level driven into the hillside.

Historical usage

Opencast working is one of the oldest mining methods in Britain, used wherever a vein or ore body ran close enough to the surface to be worked without the expense of sinking a shaft; the technique appears from prehistoric tin streaming and Roman lead working through to some of the largest surviving mine features in the country, such as the Great Opencast at Craig-y-Mwyn in Powys and Engine Vein at Alderley Edge in Cheshire, worked intermittently from the Bronze Age to the 19th century.

How it worked

Miners simply dug down and outward from the surface, following the ore as it ran, removing overburden and waste rock as they went; on a narrow, steeply dipping vein this produced a long trench or slot, while a wider or more irregular ore body could be opened into a broad pit or canyon-like cutting many metres deep.

Why it was used

Opencast working avoided the cost, danger and technical difficulty of sinking and timbering a shaft, and let miners follow visible surface indications of ore directly — the obvious, cheapest way to work a deposit for as long as it stayed within practical digging depth.

Risks & limitations

Opencast working could only reach as deep as was practical to dig and drain without pumping machinery; once a vein ran on below that depth, a mine had to convert to underground working via a shaft or adit, or abandon the ground altogether. The steep, unstable sides of an old opencast working are also a lasting safety hazard long after mining has ended.

Regional variation

Closely related to, but distinct from, hushing, which used a controlled release of water to strip surface material rather than direct digging, and from a Derbyshire rake, whose long, narrow, vein-following opencast trench is a specific regional feature type in its own right.

Images

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Craig-y-Mwyn Mine — Powys (well documented example)
  The mine's own recorded workings explicitly describe the extensive Great Opencast.
• Vitifer Mine (Birch Tor and Vitifer) — Devon (well documented example)
  The mine's own recorded workings explicitly describe extensive surface opencast pits alongside underground vein mining.

Sources

1. (primary) Engine Vein opencast copper mine, 150m north of Warden's Cottage, Nether Alderley, Cheshire East — Historic England (Scheduled Monument record)
2. (secondary) Lead — Out of Oblivion

Record created: 22 August 2026 · Last researched: 22 August 2026