The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely.

[4][5] Limonite is named for the Ancient Greek word λειμών (leimṓn [leː.mɔ̌ːn]), meaning "wet meadow", or λίμνη (límnē [lím.nɛː]), meaning "marshy lake", as an allusion to its occurrence as bog iron ore in meadows and marshes.

In thin section it appears as red, yellow, or brown and has a high index of refraction, 2.0–2.4.

Roasting the limonite changed it partially to hematite, producing red ochres, burnt umbers and siennas.

In another example the deeply weathered iron formations of Brazil served to concentrate gold with the limonite of the resulting soils.

Limonite was one of the earliest materials used as a pigment by humans, and can be seen in Neolithic cave paintings and pictographs.

The ore was then pounded as it was heated above 1250 °C,[22] at which temperature the metallic iron begins sticking together and non-metallic impurities are thrown off as sparks.

As saprolite deposits have been exhausted in many mining sites, limonite has become the most prominent source of nickel for use in energy dense batteries.