Blaes

The Scots word for the soft, laminated, bluish-grey shale and mudstone that lies between the workable seams — Barrowman's 1886 glossary gives it as 'shale; laminated clay; indurated mud'. It is grammatically a plural, from the adjective blae, blue-grey, and it names the rock a Scottish miner spent most of his working life looking at: the roof over his head, the parting in a dirty seam, and the bulk of what went up the pit as waste.

Historical usage

The word is recorded from at least 1724, when a survey of Culross reported that 'the mettals I discovered were a coarse free stone and blaes', and it stayed in general Scottish use through the whole industrial period. The Edinburgh Statistical Account of 1845 has limestone 'called by the workmen blaes' alternating with bituminous shale; Barrowman fixed it in the standard 1886 glossary; the Memoirs of the Geological Survey of Scotland were still defining it in 1920 as 'mudstone, or shale in the geological sense, not containing much bituminous matter'. It spread out of the pit and into ordinary speech: by 1920 the Glasgow Herald could report a committee costing the levelling of 'the blaes heaps' without explaining the term to anybody. It appears in this archive's own material in the Lists of Mines returns, where a colliery selling blaes alongside its coal is selling brick clay, and in accident reports, where a man taking down roof blaes is doing the most routine and most lethal job underground.

How it worked

Blaes is what most of a Scottish coal or ironstone measure actually consists of. Where it forms the roof it is taken down deliberately as the face advances, because a laminated shale roof left in place will come down on its own; where it runs as a parting inside a seam it has to be picked out at the screens or washed out, and a seam with thick partings of it is what Barrowman calls dirty coal. Where a colliery had a brickworks the blaes stopped being waste and became the raw material, which is why some collieries returned it in the Lists of Mines as an output alongside the coal. Everything else went on the bing. Burnt or heated — in an oil-shale retort, in a blazing ironstone waste heap — blaes turns from blue-grey to a hard red, and the red kind found the afterlife the material is now best known for: crushed as red blaes, it surfaced running tracks and football pitches across Scotland for most of the twentieth century. A generation of Scottish footballers learned the game on the ground their grandfathers had sent up the shaft.

Why it was used

Nobody used blaes on purpose underground; it was the rock that had to be got through or got out of the way. It earned its place in the vocabulary because it needed naming constantly — in the roof, in the seam, at the screens, on the bing — and because Scotland's coal, ironstone and oil-shale fields all sat in it.

Risks & limitations

A blaes roof is the classic Scottish killer. It parts along its laminations, and a slab that has looked sound for a shift will come away without warning, especially where the joints are glazed — a lype, in the same glossary. The Durham Mining Museum's list for Riddochhill Colliery records John Walker, aged fifty-four, taking down some roof blaes in March 1907 when a piece fell and threw him against a prop; he died eight days later. Above ground the blaes bings brought their own hazards: unstable, sometimes still burning, and quarried away for hardcore until they became, as one photographer of a crumbling West Lothian bing put it, a danger to livestock.

Regional variation

General Scots, and unusual among Scottish mining words in being understood across all the coalfields rather than one district. It is spelled Blaize, Blaise, blaze, blaies and bleeze in different sources and pronounced to rhyme with blaze. English mining vocabulary has no single equivalent: the nearest are bind, batt and metal, none of which carries the colour sense the Scots word starts from. Barrowman records compounds — 'blaes and balls' for blaes with ironstone nodules in it, 'cashy blaes' for the soft coaly kind with little coherence, and 'maggie-blaes' for an inferior sulphurous ironstone — and Ayrshire used blaise by 1928 for the refuse of burnt ironstone specifically.

Related terminology

Roof Fall, Spoil Heap

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.

• Jenny Gray Colliery — Fife (well documented example)
  Named twice in this record, first in the history: “…by 1915; and the Fourteen Feet, Little Splint and Rough by 1954. Blaes was returned alongside the coal in 1915. In 1948 the colliery raised…”
• Kilrenny Oil Works — Fife (well documented example)
  Named in this record’s surface remains: “Mounds of red spent shale — blaes — and, on aerial photographs, the outlines of substantial…”
• Meiklehill Colliery — East Dunbartonshire (well documented example)
  Named in this record’s current condition: “…been redeveloped as all-weather football pitches, alongside an older blaes pitch left derelict.”
• Lochgelly Colliery — Fife (well documented example)
  The 1915 official return lists blaes among this colliery's output, alongside the gas, household, manufacturing and steam coal — the Scots word for the shale that comes up with the coal.

Sources

1. (primary) Glossary of Scotch Mining Terms — James Barrowman (1886), via Scottish Mining Website
2. (secondary) Blaes — Scottish Shale glossary — Scottish Shale
3. (secondary) Blaes, n.2, pl. — Scottish National Dictionary — Dictionaries of the Scots Language

Record created: 10 September 2026 · Last researched: 10 September 2026