Definition

Iron is a mineral which can form inside a rock due to a chemical replacement or deposited directly as a sediment. The color of iron varies from red to yellowish brown. Iron sandstone is also called Ironstone. Ironstone is a sedimentary rock which can be formed by both processes. This rock type contains a substantial proportion of an iron compound from which iron can be smelted commercially. 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

Characteristics

Some factors on which it can be recognized:

• The texture is clastic.
• The clasts are visible with the naked eye and between 0.06 mm and 2 mm.
• It is a medium hard rock with a toughness of 6-7.
• Its color is brown to red.
• Its clast compose of quartz or feldspar and iron is present.
• It is rough to touch.

References

• 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