limonite

Limonite is characterized by its distinct ochre or yellow-brown hue, often associated with the weathering of other iron-bearing minerals. In a geological context, it is viewed as a secondary mineral, meaning it forms from the alteration of primary minerals like pyrite or magnetite through oxidation and hydration.

Because it is a mineral substance, it is treated as an uncountable mass noun. To refer to specific quantities or distinct samples, speakers must use partitive constructions such as a sample of limonite or a deposit of limonite.