Glenboig Fireclay Mines

Overview

An ordinary Lanarkshire village that lined the furnaces of the world. Glenboig's fireclay was so nearly free of iron and lime that its bricks would not crack under repeated firing, and by 1900 the company working it was reckoned the largest fireclay concern on earth, turning out a quarter of a million bricks a day.

History

Fireclay brickmaking began around Glenboig in the 1830s, with production at Cardowan from 1833-34 and the Glenboig Fire Brick and Tile Works under John Thomson from 1843, its Old Works built beside the Monkland and Kirkintilloch railway. When Thomson's partnership dissolved in 1865 James Dunnachie took control, forming the Glenboig Fire-Clay Company with John Hurll and John Young; in 1872 Dunnachie split away and built the Star Works immediately next door, so that two rival firms worked the same clay side by side. They merged in 1882 as the Glenboig Union Fireclay Company Limited with Dunnachie as managing director, and went on to acquire works at Cumbernauld, Gartcosh and Gartverrie. Dunnachie was the maker of the business twice over: as an organiser, and as the inventor of a gas-fired kiln patented in 1891 that cut fuel use by more than half and brought firing time down from days to under a day. By 1890 the company was producing about 100,000 bricks daily and sending more than a million a year to Germany, Russia and Belgium alone.

Geology

The fireclay lies in the Carboniferous Coal Measures as seatearth — the fossil soil beneath a coal seam, leached of its soluble minerals by the forest that grew in it. That leaching is exactly what makes a good fireclay, and Glenboig's was unusually well leached: remarkably free of the bases, iron oxide and lime especially, that cause a firebrick to soften and break down under heat. Bricks made from it would take repeated extreme firing without cracking, which is why steelmakers wanted them and why an ordinary-looking clay under a Lanarkshire field became a world commodity.

Geological setting: Sedimentary Beds and Seams (well documented example)

Workings

Underground mining of the fireclay seams rather than open digging, on a scale that ran under much of the parish — the Glenboig-Inchneuk complex alone was extensive. Fourteen abandonment plans for the Glenboig mines survive in the national catalogue, lodged by the Glenboig Union Fireclay Company and its successors, with abandonment dates running from 1932 to 1981. At surface the clay went to the Old Works and the Star Works, and after 1891 through Dunnachie's gas-fired kilns.

Closure

The Glenboig-Inchneuk mine, worked from the 1880s, was abandoned in 1956; other fireclay mines in the group ran on into the 1980s, the last abandonment plans dated 1981. The industry went the way of the furnaces it supplied.

What remains

The works have gone and Glenboig is a residential village; the ground is undermined and the sites cleared. Glenboig bricks, however, are everywhere — they turn up in furnace linings and buildings across the world and are collected for their stamps.

Little on the ground. The most numerous survivals are the bricks themselves, stamped GLENBOIG or with the Star Works mark, found wherever the company exported.

Redevelopment

Housing and open ground; the loch at Garnqueen and the village park occupy part of the old industrial landscape.

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.

• Fireclay brickmaking began around Glenboig in the 1830s, with production at Cardowan from 1833-34 and the Glenboig Fire Brick and Tile Works under John Thomson from 1843. ¹
• James Dunnachie took control in 1865 with John Hurll and John Young, split away to build the Star Works in 1872, and became managing director when the two firms merged as the Glenboig Union Fireclay Company Limited in 1882. ¹
• The Glenboig fireclay was remarkably resistant to extreme heat and remarkably free of bases such as iron oxide and lime, so that its bricks did not crack after repeated firing — a decisive advantage in steel furnaces. ¹
• By 1890 the company produced about 100,000 bricks a day, and more than a million a year went to Germany, Russia and Belgium. ¹
• Dunnachie patented a gas-fired kiln in 1891 which saved upwards of 50 per cent of fuel and cut firing time from days to eighteen to twenty-four hours. ¹
• The company won 22 prize medals at international exhibitions, including gold at Paris in 1878 and a diploma of honour at Brussels in 1897. ¹
• The Glenboig-Inchneuk mine complex, first worked in the 1880s, was abandoned in 1956; abandonment plans for the Glenboig fireclay mines run from 1932 to 1981. ^2,3

Photographs & further reading

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

Images

Sources

1. (primary) Glenboig Union Fireclay Company — history — Scotland's Brick and Tile Manufacturing Industry
2. (primary) Mine plans SWR2577 and SW209: Hopewell, Wimberry, Cannop and associated gales — British Geological Survey / Mining Remediation Authority mine plans catalogue
3. (secondary) Glenboig Mine — Scottish Cave and Mine Database
4. (secondary) Glenboig Union Fireclay Co — Grace's Guide

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