Gunnies

The open void left behind in a mine once a vertical or near-vertical ore lode has been stoped out along its length — from the Cornish gonis, meaning 'working'.

Historical usage

A genuinely old term, in continuous Cornish use from medieval mining through to the 19th and early 20th centuries; where early miners worked a lode by following it straight down from the surface, the resulting trench is often distinguished as an 'open-work', and the presence of old open-works is frequently the earliest surviving evidence of mining in an area at all.

How it worked

As a lode was worked out along its width and length, the excavated space behind the miners simply remained open unless deliberately filled, forming a gunnies running along the line of the vein. Where such a void broke through to the surface, it was known as a coffin or goffen; underground, old gunnies could reach enormous size — an account from St Agnes in 1934 described one large enough to have 'contained a decent sized cathedral', some 150-200 feet deep.

Why it was used

Recognising and respecting old gunnies mattered for basic survival underground: a lode already worked out and left open told later miners exactly where not to blast blind, and warned them of large void space nearby that might be flooded, unstable, or both.

Risks & limitations

A gunnies is exactly the kind of large void that makes old workings dangerous long after mining stops: unsupported spans could and did collapse — Dolcoath's own 1901 records warned of 'immense gunnies' still slowly moving 73 years after a major 1828 collapse — and a gunnies that had silently flooded was lethal to break into by accident, the exact mechanism behind the 1893 Wheal Owles disaster elsewhere in this site's own records, where breaking into old flooded workings killed nineteen men and a boy in minutes.

Regional variation

The Cornish mining village of Gunnislake takes part of its name from this same word. Old, disused gunnies were also often deliberately backfilled with waste rock (deads) as later working progressed, both to disperse waste and to reduce the hazard of leaving a large void open indefinitely.

Sources

1. (secondary) Glossary — Cornish Mining World Heritage Site
2. (secondary) Glossary of Mining Terms — Open University Geological Society (South West Branch)
3. (secondary) Gunnies — Wikipedia

Record created: 20 August 2026 · Last researched: 20 August 2026