John G Stein leased the fireclay at Milnquarter, Bonnybridge from Zetland Estates in 1887 and opened Milnquarter Fireclay Mine. In 1891 he went into partnership with Malcolm Cockburn and opened Milnquarter Brickworks, Bonnybridge. In 1896 Stein became sole partner and the company was incorporated as John G Stein & Co in 1905.

Anchor Works opened in the 1890s and Castlecary Works opened in 1899. Its kiln was the longest in the world at over 300 metres. Manuel Works, near Whitecross was opened in 1928 and closed 28 December 2001. In 1931 the Anchor Works were closed. In the late 1960s, Milnquarter was also closed in late 1960s and by October 1971 mine had ceased working.

In 1970 J G Stein & Co merged with General Refractories Ltd and as GR-Stein became a subsidiary of Hepworth Ceramic Holdings Ltd