Goetiittia

Goetiittia is a mineral belonging to the oxide class, specifically a hydrated iron oxide. Its chemical formula is FeO(OH) or Fe₂O₃·H₂O. Goetiittia is a common mineral found in various geological environments, often forming as a secondary mineral through the weathering of iron-bearing primary minerals. It is also a significant component of bog iron ores and is found in soils and sediments.

The color of goetiittia typically ranges from yellow to brown to reddish-brown, depending on its purity and the presence of impurities. It often exhibits a fibrous or botryoidal habit, but can also occur as earthy masses or in crystalline forms. The hardness of goetiittia on the Mohs scale is typically between 4.5 and 5.5, making it relatively soft. It has a specific gravity of around 4.3.

Goetiittia plays a role in several natural processes. Its formation is indicative of oxidizing and relatively low-temperature conditions. It can contribute to the coloration of rocks and soils. Historically, goetiittia has been used as a pigment, known as yellow ochre or brown ochre, for paints and dyes. It is also an important ore of iron, although often not the primary source. In some contexts, goetiittia can form concretions or nodules within soils and sediments.