Devon Great Consols

Overview

Devon Great Consols was, for a time, the largest copper mine in the world, and later the largest producer of arsenic — a byproduct that kept it profitable long after its copper had stopped being competitive. Now part of the Cornwall and West Devon Mining Landscape World Heritage Site, it also carries a serious legacy of arsenic contamination.

History

A lease was taken from the Duke of Bedford on 26 July 1844 by six investors led by Josiah Hugh Hitchens — among them the father of the designer William Morris, whose son later served as a company director from 1871 to 1875. Working initially as North Bedford Mines, or Wheal Maria, the venture struck a rich copper vein at about 20 fathoms depth within months, and the company was formally incorporated as the Devonshire Great Consolidated Copper Mining Company on 25 March 1845. Nearly 90,000 tons of copper ore were raised in the first six years alone, and by 1864 — with the mine down to 200 fathoms and employing 1,284 people — it was considered the most productive copper mine in the world. The mine built its own 5-mile railway to Morwellham Quay on the River Tamar, completed in November 1858, with its own locomotives and wagons. When copper prices collapsed in the mid-1860s as Australian, American and Chilean ore reached the market, many smaller Devon mines failed outright; Devon Great Consols survived by diversifying into arsenic production from 1867, becoming the 19th century's largest arsenic producer. The mine finally closed in 1903, having produced around 700,000 tons of copper ore and 72,000 tons of refined arsenic over its roughly 60-year life; smaller-scale 20th-century rework extracted tin and tungsten from the dumps, continuing sporadically as late as the 1970s, with arsenic processing on the site continuing until 1930.

Geology

The mine worked rich copper lodes within the Tamar Valley, alongside significant quantities of mundic (arsenical pyrite) that made the site's later arsenic industry possible.

Workings

Workings reached around 200 fathoms (roughly 360 m) by 1864. Ore and refined arsenic moved out via the mine's own 5-mile railway to Morwellham Quay, opened in 1858 and worked with the company's own locomotives.

Closure

The mine closed in 1903 as the ore and arsenic that had sustained it for six decades were worked out; smaller-scale reworking of the dumps for tin, tungsten and residual arsenic continued intermittently well into the 20th century.

What remains

The site is part of the Cornwall and West Devon Mining Landscape UNESCO World Heritage Site and reopened to public access in 2009. A 2020 University of Plymouth study found arsenic concentrations at 98 sampled locations across the site exceeding screening levels, and the land remains heavily contaminated in places.

Surviving structures include mine captains' houses (Grade II listed, 13 January 1986), the Wheal Josiah arsenic works and associated cottages (Grade II listed, 23 January 1987), and 20th-century arsenic works designated a scheduled monument on 24 July 2002.

Redevelopment

The site is open for public access and forms part of the wider Tamar Valley Mining Heritage Project; no other redevelopment has taken place given the ongoing arsenic contamination.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• Over its roughly 60-year working life the mine produced around 700,000 tons of copper ore and 72,000 tons of refined arsenic, and was considered the most productive copper mine in the world around 1864. ¹
• A 2020 University of Plymouth study found arsenic concentrations at 98 sampled locations across the site exceeding Category 4 Screening Levels, and the land remains heavily contaminated in places. ¹

Photographs & further reading

This page doesn't try to reproduce everything — these are the best original sources found for this mine.

Images

Sources

1. (secondary) Devon Great Consols — Wikipedia
2. (primary) Early 20th century arsenic works at the Devon Great Consols Mine, Gulworthy — Historic England