Ilmenite - Encyclopedia

    Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Trigonal
    Chemistry : FeTiO₃
    Rarity : Very common

Ilmenite is a common accessory mineral in basic magmatic rocks (gabbros, diorites and especially anorthosites, where it can concentrate by magmatic segregation to form large exploited masses), in certain metamorphic rocks (gneiss and granulites), in nepheline syenites, more rarely in hydrothermal veins and pegmatites. Unalterable under atmospheric conditions, ilmenite is very widespread in alluvium where it is commonly exploited. Ilmenite constitutes two series, one complete towards the magnesium pole, geikielite, the other partial towards the manganiferous pole, pyrophanite. The presence of vanadium is common. Its name comes from its type locality : the Ilmen Mountains (Russia). Ilmenite occurs in thick tablets with rhombohedral facies, sometimes lamellar micaceous, in shapeless inclusions, rarely in compact granular masses or in aggregates. The luster is strong, the color iron black to grayish black with gray-black dust ; it is weakly magnetic (those attractable by the hand magnet contain exsolutions of magnetite). Imenite is the main ore of titanium, less rich in this metal than rutile, but constituting significantly more frequent and larger accumulations.

Main photo : Ilmenite from Rønholt, Bamble, Norway © Oivind Thoresen

Twins are known on {0001} and {101-1}.

No fakes recorded for this mineral species. Difficult to separate from hematite without chemical analysis or indication of the presence of titanium (rutile or titanite epitaxies for example).