Definition of "ironstone"

During my stay at Kamalia there was a smelting furnace at a short distance from the hut where I lodged, and the owner and his workmen made no secret about the manner of conducting the operation, and readily allowed me to examine the furnace, and assist them in breaking the ironstone.

1815, Mungo Park, chapter XXI, in Travels in the Interior of Africa‎, volume II, Cassell, published 1893

The trees like this barren ironstone formation. It's well they do, for nothing else does.

1924, D. H. Lawrence, chapter 3, in The Boy in the Bush, New York: Viking, published 1972, page 41

While I listen I sniff in the cordite fumes. Ironstone chipped against ironstone invokes a spark and a wisp of the same heady smoke.

1977, J. M. Coetzee, In the Heart of the Country, Penguin, published 1982, page 61

Just before Bloworth Crossing, you'll walk a short distance along the trackbed of the old mineral railway that connected the old ironstone mines at Rosedale with the blast furnaces of Middlesbrough.

2019, Alan Staniforth, Cleveland Way, page 64

More than 50 percent of the collection from Hall’s brothel is ironstone and porcelain. White ironstone tablewares became popular in the late 1850s, and the high percentage of this ware suggests attention to fashion.

2000, Donna J. Seifert, Elizabeth Barthold O'Brien, Joseph Balicki, “Mary Ann Hall's first-class house: the archaeology of a capital brothel”, in Robert A. Schmidt, Barbara L. Voss, editors, Archaeologies of Sexuality, London: Routledge, page 120