Tailings

The finely ground waste material left over once ore has been crushed and its valuable mineral extracted — a slurry of rock fragments and residual chemicals that historically had to be dumped, discharged into a stream, or, in later, more regulated practice, stored in an engineered lagoon or dam.

Historical usage

Tailings disposal has been a byproduct of ore processing for as long as ore has been crushed and dressed, but the method changed markedly over time. Historically, tailings were often discharged directly into the nearest stream or river, or simply tipped into heaps and valleys close to the mill — a practice that left lasting metal contamination in watercourses across British mining districts. From the mid-20th century onward, tightening environmental regulation increasingly required tailings to be contained in purpose-built lagoons or dams rather than released or dumped freely; Wheal Maid's valley in Cornwall, converted into a series of engineered tailings lagoons through the 1970s and 1980s to store waste from the nearby Mount Wellington and Wheal Jane mines, is a well-documented example of this later, more contained approach.

How it worked

After ore was crushed and the valuable mineral separated out — traditionally by gravity methods such as jigging and buddling, later by froth flotation — the remaining fine-grained waste, a slurry of ground rock, water and residual processing chemicals, was carried away from the mill, historically by gravity flow into a nearby stream or spoil ground, and in later practice by pipeline into a contained lagoon or dam designed to hold it.

Why it was used

Separating usable ore from waste rock is inherent to almost all mineral processing, so tailings disposal was never optional — only the method changed. As processing technology improved and made it economic to work lower-grade ore, the volume of tailings produced for each tonne of metal recovered tended to increase, making disposal and, later, containment an ever larger part of a mine's overall footprint.

Risks & limitations

Tailings retain a residual proportion of the target metal along with other heavy metals, and where the ore was sulphide-bearing, contain pyrite that continues to oxidise for decades after deposition, generating acidic, metal-laden drainage — the process documented in detail at Wheal Maid, now one of the most scientifically studied contaminated legacy sites in Britain. Historic streamside dumping left many British mining districts with long-term watercourse pollution, and even engineered tailings dams require ongoing management to prevent leakage or failure.

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.

• Carrock Fell Mine — Cumbria (well documented example)
  The mine's own recorded current condition explicitly describes a tailings lagoon bulldozed and graded after the site's 1988 closure.
• Conlig and Whitespots Lead Mines — County Down (well documented example)
  The mine's own recorded workings and surface remains explicitly describe surviving tailings impoundments.
• Esgair Mwyn Mine — Ceredigion (well documented example)
  The mine's own recorded current condition and surface remains explicitly describe a fine tailings tip estimated at around 60,000 tonnes.
• Mount Wellington Mine — Cornwall (well documented example)
  The mine's own recorded history and closure notes explicitly describe the Wheal Maid tailings lagoons that received the mine's waste.
• Mulreesh Lead Mines — Argyll and Bute (well documented example)
  The mine's own recorded current condition explicitly describes tailings still visible among the site's surviving remains.
• Wheal Friendship — Devon (well documented example)
  The mine's own recorded history and closure notes explicitly describe tribute working of dumps and tailings continuing into the 1950s.
• Wheal Maid — Cornwall (well documented example)
  The mine's own recorded history, geology, closure notes, current condition and surface remains all explicitly describe its tailings lagoons.

Sources

1. (secondary) Evolution of Sulfidic Legacy Mine Tailings: A Review of the Wheal Maid Site, UK — Minerals (MDPI), peer-reviewed journal
2. (secondary) Wheal Maid — Wikipedia

Record created: 24 August 2026 · Last researched: 24 August 2026