(named after the deposit in the Il’men Mountains, where ilmenite was first found), a mineral whose composition is FeTi03 (47.34 percent FeO and 52.66 percent Ti02). Its composition is not constant. Fe2+ is replaced isomorphically by Mg2+ and Mn2+ ; correspondingly, ilmenite may contain up to 17 percent MgO (magnesian ilmenite) and 14 percent MnO (manganoan ilmenite). Admixtures of Nb, V, Cr, Co, and Ni are also known.
Ilmenite crystallizes in the trigonal system; it sometimes forms complex rhombohedral crystals and, more frequently, granular masses and continuous agglomerates of black color with a bright submetallic luster. Nontransparent and magnetic, ilmenite has a hardness of 5–6 on the mineralogical scale and a density of 4,600 to 4,800 kg/m2. The crystalline structure of ilmenite is similar to that of hematite, which often occurs in ilmenite as a solid solution or as a product of its decay. In the crystallization of natural ore melts high in Ti with an excess of FeO and Fe203, so-called titanomagnetites are formed. Deposits of ilmenite (and titanomagnetites) are connected with gabbroid type igneous rocks. It is known as a magmatic mineral in kimberlites, forms agglomerates in alkaline syenite pegmatites, and accumulates in placer deposits. In the USSR deposits are found in the southern and central Urals, in the Altai, on the Kola Peninsula, and in the Ukraine. Ilmenite is a valuable ore for obtaining titanium and its derivatives, which are widely used in metallurgy and the chemical and other industries.
G. P. BARSANOV