Scottish Slate

Scottish slate is natural roofing slate from quarries in Scotland. It covers a large share of the country's historic roofs, but commercial quarrying ended in 1965, so repairs today depend on reclaimed Scottish slate or imported substitutes. Efforts to reopen historic sources began in the 2020s.

Types

Scottish roofing slate is usually grouped into three types:

• West Highland slate, from more than 64 sites in Argyll and Inverness-shire centred on Ballachulish, Easdale, Cullipool and Tayvallich. It is the darkest type, dark grey to blue-black, often with a rippled surface and small cubes of iron pyrite.
• Highland Border slate, from about 80 quarries in a strip running from Bute to Dunkeld along the edge of the Highlands. Colours range from reddish-purple grey to greenish grey; striped red and green slates from Aberfoyle have been nicknamed "tartan".
• Macduff slate, from a few hundred mostly small quarries around the Hills of Kirkney and Tillymorgan in Aberdeenshire and in Banffshire. It is typically grey with a flat, slightly rough surface.

History

The first written reference to Easdale slate dates from 1554. Commercial extraction on the Slate Islands is recorded from the 17th century, and Easdale slate roofed Castle Stalker in Appin in 1631 and Ardmaddy Castle in 1676. The Marble and Slate Company of Netherlorn was formed in 1745, when over a million slates were made; pumping machinery later allowed quarrying below sea level, and output reached about 5 million slates a year by 1800. The Ellenabeich quarry was worked to a depth of 250 ft (about 76 m).

A tidal flood in 1881 drowned the Easdale quarries, and output never recovered; the industry lost ground to Ballachulish and then to Welsh slate, and the last commercial shipment from Easdale left in 1911. In the 19th century Scottish slate was exported to the United States, Australia and New Zealand. The Cullipool quarries on Luing were the last to close, in 1965.

Supply today

The only genuine Scottish slate now available is reclaimed from older buildings, and that supply is shrinking. Most slate used in Scotland is imported, mainly from Spain. A 2024 British Geological Survey report funded by Historic Environment Scotland identified 32 historic sources with potential for development. At Cullipool, minerals planning consent was granted in 2024 and the Isle of Luing Community Trust secured £1.75 million from the Scottish Government, and test production was announced for summer 2026.

Conservation

Matching the colour, texture and thickness of the original slate is important on listed and historic buildings, and reclaimed slates of the same type are usually preferred over new imports for repairs.