Ilmenite is a titanium-iron(II) oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used as white pigment in paints, printing inks, fabrics, plastics, paper, sunscreen, food and cosmetics.

Structure and properties

Ilmenite is a heavy (specific gravity 4.7), moderately hard (Mohs hardness 5.6 to 6), opaque black mineral with a submetallic luster.

Ilmenite is distinguished from hematite by its less intensely black color and duller appearance and its black streak, and from magnetite by its weaker magnetism. Gregor named this mineral manaccanite. The same mineral was found in the Ilmensky Mountains, near Miass, Russia, and named ilmenite. and in some highly differentiated felsic rocks ilmenites may contain significant amounts of pyrophanite molecules.

At temperatures above , there is a complete solid solution between ilmenite and hematite. There is a miscibility gap at lower temperatures, resulting in a coexistence of these two minerals in rocks but no solid solution. Ilmenite containing 6 to 13 percent is sometimes described as ferrian ilmenite.

Ilmenite alters or weathers to form the pseudo-mineral leucoxene, a fine-grained yellowish to grayish or brownish material enriched to 70% or more of .

Paragenesis

Ilmenite is a common accessory mineral found in igneous and high-grade metamorphic rocks. or in combination with plagioclase and apatite (nelsonite).

Magnesian ilmenite is formed in kimberlites as part of the MARID association of minerals (mica-amphibole-rutile-ilmenite-diopside) assemblage of glimmerite xenoliths. Manganiferous ilmenite is found in granitic rocks

Many mafic igneous rocks contain grains of intergrown magnetite and ilmenite, formed by the oxidation of ulvospinel. Ilmenite and titanium dioxide are used in the production of titanium metal.

Titanium dioxide is most used as a white pigment, and the major consuming industries for TiO<sub>2</sub> pigments are paints and surface coatings, plastics, and paper and paperboard. Per capita consumption of TiO<sub>2</sub> in China is about 1.1 kilograms per year, compared with 2.7 kilograms for Western Europe and the United States.

thumb|Estimated world production of titanium concentrate by mineral source in metric tons, 2015–2019. Titanium concentrate is mainly obtained from the processing of ilmenite mineral, followed by titaniferous slags and natural rutile.

Titanium is the ninth most abundant element on Earth and represents about 0.6 percent of the Earth's crust. Ilmenite is commonly processed to obtain a titanium concentrate, which is called "synthetic rutile" if it contains more than 90 percent TiO<sub>2</sub>, or more generally "titaniferous slags" if it has a lower TiO<sub>2</sub> content. More than 80 percent of the estimated global production of titanium concentrate is obtained from the processing of ilmenite, while 13 percent is obtained from titaniferous slags and 5 percent from rutile.

Ilmenite can be converted into pigment-grade titanium dioxide via either the sulfate process or the chloride process. Ilmenite can also be improved and purified to titanium dioxide in the form of rutile using the Becher process.

Ilmenite ores can also be converted to liquid iron and a titanium-rich slag using a smelting process.

Steelmakers use ilmenite ore as a flux to line the blast furnace hearth refractory.

Ilmenite can be used to produce ferrotitanium via an aluminothermic reduction.

Feedstock production

{| class="wikitable" style="float:right; clear:right; margin:0 0 .5em 1em;"

|+Various ilmenite feedstock grades.

|-

! Feedstock || Content || Process

|-

! || (%) ||

|-

| Ore || <55 || Sulfate

|-

| Ore || >55 || Chloride

|-

| Ore || <50 || Smelting (slag)

|-

| Synthetic rutile || 88–95 || Chloride

|-

| Chloride slag || 85–95 || Chloride

|-

| Sulfate slag || 80 || Sulfate

|}

{| class="wikitable" style="float:right; clear:right; margin:0 0 .5em 1em;"

|+Estimated contained . <br> production<br><small>(Metric tpa x 1,000,</small><br><small>ilmenite & rutile)</small>

|-

! Year || 2011 || 2012–13

|-

! Country || USGS || Projected

|-

| Australia || 1,300 || 247

|-

| South Africa || 1,161 || 190

|-

| Mozambique || 516 || 250

|-

| Canada|| 700||

|-

| India || 574||

|-

| China || 500||

|-

| Vietnam || 490||

|-

| Ukraine || 357||

|-

| Senegal || - || 330

|-

| Norway || 300||

|-

| United States || 300||

|-

| Madagascar || 288||

|-

| Kenya || - || 246

|-

| Sri Lanka || 62 ||

|-

| Sierra Leone || 60||

|-

| Brazil || 48||

|-

| Other countries || 37||

|-

| Total world || ~6,700 || ~1,250

|}

Most ilmenite is recovered from heavy mineral sands ore deposits, where the mineral is concentrated as a placer deposit and weathering reduces its iron content, increasing the percentage of titanium. However, ilmenite can also be recovered from "hard rock" titanium ore sources, such as ultramafic to mafic layered intrusions or anorthosite massifs. The ilmenite in layered intrusions is sometimes abundant, but it contains considerable intergrowths of magnetite that reduce its ore grade. Ilmenite from anorthosite massifs often contains large amounts of calcium or magnesium that render it unsuitable for the chloride process.

The proven reserves of ilmenite and rutile ores are estimated to be between 423 and 600 million tonnes of titanium dioxide. The largest ilmenite deposits are in South Africa, India, the United States, Canada, Norway, Australia, Ukraine, Russia and Kazakhstan. Additional deposits are found in Bangladesh, Chile, Mexico and New Zealand.

Australia was the world's largest ilmenite ore producer in 2011, with about 1.3 million tonnes of production, followed by South Africa, Canada, Mozambique, India, China, Vietnam, Ukraine, Norway, Madagascar and the United States.

The top four ilmenite and rutile feedstock producers in 2010 were Rio Tinto Group, Iluka Resources, Exxaro and Kenmare Resources, which collectively accounted for more than 60% of the world's supplies.

The world's two largest open cast ilmenite mines are:

  • The Tellnes mine located in Sokndal Municipality, Norway, and run by Titania AS (owned by Kronos Worldwide Inc.) with 0.55 Mtpa capacity and 57 Mt contained reserves.
  • The Rio Tinto Group's Lac Tio mine located near Havre Saint-Pierre, Quebec, in Canada with a 3 Mtpa capacity and 52 Mt reserves.

Major mineral sands-based ilmenite mining operations include:

  • Richards Bay Minerals in South Africa, majority-owned by the Rio Tinto Group.
  • Kenmare Resources' Moma mine in Mozambique.
  • Iluka Resources' mining operations in Australia, including Murray Basin, Eneabba and Capel.
  • The Kerala Minerals & Metals Ltd (KMML), Indian Rare Earths (IRE), VV Mineral mines in India.
  • TiZir Ltd.'s Grande Cote mine in Senegal
  • QIT Madagascar Minerals mine, majority-owned by the Rio Tinto Group, which began production in 2009 and is expected to produce 0.75 Mtpa of ilmenite, potentially expanding to 2 Mtpa in future phases.

Attractive major potential ilmenite deposits include:

  • The Karhujupukka magnetite-ilmenite deposit in Kolari, northern Finland, with around 5 Mt reserves and ore containing about 6.2% titanium.
  • The Balla Balla magnetite-iron-titanium-vanadium ore deposit in the Pilbara of Western Australia, which contains 456 million tonnes of cumulate ore horizon grading 45% , 13.7% and 0.64% , one of the richest magnetite-ilmenite ore bodies in Australia
  • The Coburn, WIM 50, Douglas, Pooncarie mineral sands deposits in Australia.
  • The Magpie titano-magnetite (iron-titanium-vanadium-chrome) deposits in eastern Quebec of Canada with about 1 billion tonnes containing about 43% Fe, 12% TiO<sub>2</sub>, 0.4% V<sub>2</sub>O<sub>5</sub>, and 2.2% Cr<sub>2</sub>O<sub>3</sub>.
  • The Longnose deposit in Northeast Minnesota is considered to be "the largest and richest ilmenite deposit in North America."

thumb|Worldwide mining of the titanium-containing minerals ilmenite and rutile in thousand tonnes of TiO<sub>2</sub> equivalent by country, in 2020.

In 2020, China had by far the highest titanium mining activity. About 35 percent of the world's ilmenite is mined in China, representing 33 percent of total titanium mineral mining (including ilmenite and rutile). South Africa and Mozambique are also important contributors, representing 13 percent and 12 percent of worldwide ilmenite mining, respectively. Australia represents 6 percent of the total ilmenite mining and 31 percent of rutile mining. Sierra Leone and Ukraine are also big contributors to rutile mining. Ilmenite has been targeted for ISRU water and oxygen extraction due to a simplistic reduction reaction which occurs with CO and H<sub>2</sub> buffers. The European Space Agency's VMMO mission, expected to launch in 2028, intends to map the distribution of ilmenite on the Moon.

Sources

References