Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely banded, nonbanded, and noncherty sedimentary rocks of post-Precambrian age. The Precambrian deposits, which have a different origin, are generally known as banded iron formations. The iron minerals comprising ironstones can consist either of oxides, i.e. limonite, hematite, and magnetite; carbonates, i.e. siderite; silicates, i.e. chamosite; or some combination of these minerals.
Freshly cleaved ironstone is usually grey. The brown external appearance is due to oxidation of its surface. Ironstone, being a sedimentary rock is not always homogeneous, and can be found in a red and black banded form called tiger iron, sometimes used for jewelry purposes.
Ironstone as a source of iron
Ironstone, although widespread, is a limited source of iron (Fe). Historically, most of British iron originated from ironstone, but it is now rarely used for this purpose because it is far too limited in quantity to be an economic source of iron ore.
Ironstone is used as a component in some ceramics, commonly known as "ironstone china". Josiah Wedgwood also manufactured a "stoneware" china in the 19th century. It was commonly used for heavy-duty dinner services in the 19th century. Charles James Mason (son of the potter Miles Mason) took out a patent for "Mason's Ironstone China" in 1813. Ironstone china was very popular during the 1970s.
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- U.S. Bureau of Mines Staff (1996) Dictionary of Mining, Mineral, & Related Terms. Report SP-96-1, U.S. Department of Interior, U.S. Bureau of Mines, Washington, D.C.
- Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ISBN 0-922152-76-4
- G. Bernard Hughes, English and Scottish Earthenware, Abbey Library
- Keele University "Mason's Patent Ironstone China",""
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