ilmenisi

Ilmenisi is the mineral species most commonly known as ilmenite, an iron titanium oxide with the approximate chemical formula FeTiO3. It is a dense, opaque mineral that typically appears black to brownish-black with a metallic to submetallic luster. Its streak is usually brownish, and it has a Mohs hardness around 5 to 6. Ilmenite often occurs as granular or platy grains and can be part of solid-solution series with hematite in which titanium is progressively substituted by iron.

Geologically, ilmenite forms in a range of environments. It is a common accessory mineral in igneous rocks, particularly basalt and related rocks, and in some metamorphic rocks. It also concentrates in heavy-mineral sands along coastlines, yielding large beach and dune deposits that are economically important. In such deposits, ilmenite coexists with magnetite, titanomagnetite, and other oxide or silicate minerals.

Economically, ilmenite is the principal ore of titanium. It can be processed to produce titanium dioxide (TiO2), a pigment widely used in paints, plastics, and paper. Titanium metal can be extracted from ilmenite via reduction processes such as the Kroll method, though this is more energy-intensive. The distribution of ilmenite deposits supports major mining industries in several countries, including those with heavy-mineral sands along coasts and in inland igneous stocks.

Name and origin: the term ilmenite derives from the Ilmen Mountains in the Ural region, where the mineral was first described in the 18th century. The mineral is part of the ilmenite-hematite solid-solution system, reflecting its iron-rich end-member and titanium-bearing composition.