maghemiitin

Maghemiite is a mineral with the chemical formula Fe(III)2O3 or FeO(OH). It is a naturally occurring iron oxide that is a member of the iron oxide-hydroxide group. Maghemiite is sometimes referred to as gamma-iron(III) oxide. It forms in a variety of geological environments, including soils, sediments, and altered igneous rocks.

Crystallographically, maghemiite has a cubic structure, similar to that of magnetite. However, unlike magnetite, maghemiite has a deficiency of iron cations in its structure, making it non-stoichiometric. This structural difference leads to distinct magnetic properties. Maghemiite is ferrimagnetic, meaning it exhibits a net magnetic moment due to the antiparallel alignment of magnetic moments of its ions. Its magnetic susceptibility is generally lower than that of magnetite.

In nature, maghemiite often forms through the oxidation of magnetite or other iron-bearing minerals. This process can occur under oxidizing conditions, particularly in the upper layers of soils where weathering is active. It is also found as a byproduct of certain industrial processes involving iron.

Maghemiite is typically dark brown to black in color and has a metallic to submetallic luster. It is relatively soft, with a Mohs hardness of around 5 to 6. Due to its magnetic properties, maghemiite has found applications in various fields, including as a component in magnetic recording media and as a pigment. Its presence in soils can also influence soil properties such as water retention and nutrient availability.