Manganese

A hard, brittle metal (Mn) essential to modern steelmaking, added as ferromanganese or spiegeleisen to strip impurities from molten steel and strengthen the finished metal — a comparatively minor British industry whose entire commercial life was dictated by the rise and fall of demand from a single revolutionary technology, the Bessemer converter.

Historical usage

The earliest recorded British use of manganese ore was as a bleaching agent: from 1835, Welsh manganese was worked on a small scale for Glasgow's bleaching-powder trade, converting cotton-bleaching from a months-long process into one taking hours. That same Glasgow bleaching-powder industry gave the world its first documented case of manganese poisoning, when the physician James Couper identified severe neurological symptoms among manganese-handling employees of Charles Tennant and Co. in 1837 — decades before anyone connected the disease to occupational exposure more broadly. Real commercial demand for manganese only arrived with the Bessemer and open-hearth steelmaking processes developed from around 1870, which required manganese, as ferromanganese or spiegeleisen, to remove phosphorus, sulphur and silica from molten steel, at a rate of roughly 14 pounds for every ton produced. This transformed manganese from a curiosity into a strategic mineral: a dozen mines opened along a single manganese outcrop in Merioneth, north Wales, in 1886 alone, output from mines in Devon, Cornwall and Somerset also revived, and by the First World War manganese miners were being sought exemptions from military conscription because the mineral was considered essential to the war effort.

How it worked

Manganese ore was worked by whatever method suited its particular deposit — open opencast cutting where the ore lay near the surface, underground stoping where it ran deep or steeply, as at Hafotty in Merioneth — then crushed, hand-sorted and shipped to steelworks for smelting into ferromanganese or spiegeleisen alloy.

Why it was used

Manganese's chemical affinity for phosphorus, sulphur and silica let it strip these impurities out of molten steel during the Bessemer and open-hearth processes, without which the mass-produced steel that built the railways, ships and structures of the industrial age could not have been made to a reliable, predictable quality.

Value over time

Manganese had almost no commercial value in Britain before 1870: a brief flurry of interest in the 1830s, tied entirely to the Glasgow bleaching-powder trade, petered out within a few years once cheaper alternatives emerged. The Bessemer and open-hearth revolution in steelmaking changed that overnight from around 1870 onward, turning manganese into a genuinely strategic mineral almost by accident of chemistry — but British deposits were never rich or extensive enough to compete once the world's major manganese-producing regions were properly opened up, and by the 1890s the brief Welsh manganese boom was already over. Wartime strategic anxiety briefly revived interest twice more, in the First World War and again in planning documents drawn up during the Second, but neither led to sustained large-scale British production again.

Hazards & challenges

Chronic exposure to manganese dust and fume causes manganism, a severe and often irreversible neurological condition resembling Parkinson's disease, first identified as an occupational illness in 1837 among Glasgow bleaching-powder workers handling manganese ore — making manganese one of the very few British minerals whose principal industrial health hazard was documented before the mineral had found its major industrial use.

Risks & limitations

British manganese deposits were almost always thin, steeply dipping and difficult to work compared with the huge, shallow overseas deposits later developed in Russia, India, Brazil and South Africa, meaning the domestic industry could only ever compete during the brief window before cheap imported ore reached the market in volume — by the 1890s, most British mines, including Hafotty, had already closed.

Regional variation

Small manganese mining districts developed in Merioneth and Caernarfonshire in north Wales, the largest concentration in Britain, alongside more minor 18th- and 19th-century workings in Devon, Cornwall and Somerset; none ever approached the scale of the deposits later developed overseas.

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.

• Hafotty Manganese Mine — Gwynedd (well documented example)
  The largest of Merioneth's manganese mines, opened in 1885 to meet Bessemer-era steelmaking demand.

Sources

1. (primary) Diagnosis of manganism and manganese neurotoxicity: A workshop report — PMC / NIH
2. (secondary) Manganism — Wikipedia
3. (secondary) Merioneth Manganese: History — Hendrecoed North Wales Mining History
4. (secondary) Uses of manganese — Hendrecoed North Wales Mining History

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