Ironstone

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 ore compound from which iron (Fe) can be smelted commercially.

Not to be confused with native or telluric iron, which is very rare and found in metallic form, the term ironstone is customarily restricted to hard, coarsely banded, non-banded, and non-cherty sedimentary rocks of post-Precambrian age.

The Precambrian deposits, which have a different origin, are generally known as banded iron formations.

Ironstone, being a sedimentary rock is not always homogeneous, and can be found in a red-and-black banded form called tiger iron[broken anchor], sometimes used for jewelry purposes.

Examples include the parish churches at Kirby Bellars and South Croxton in Leicestershire, and Eydon Hall in Northamptonshire.