| Ilmenite | |
|---|---|
 Ilmenite from Miass, Ilmen Mts, Chelyabinsk Oblast', Southern Urals, Urals Region, Russia. 4.5 x 4.3 x 1.5 cm | |
| General | |
| Category | Oxide mineral |
| Formula | Iron(II) titanium oxide,FeIITiO3 |
| IMA symbol | Ilm[1] |
| Strunz classification | 4.CB.05 |
| Dana classification | 04.03.05.01 |
| Crystal system | Trigonal |
| Crystal class | Rhombohedral (3) H-M symbol: (3) |
| Space group | R3 (no. 148) |
| Unit cell | a = 5.08854(7) c = 14.0924(3) [Å]: Z = 6 |
| Identification | |
| Color | Iron-black; gray with a brownish tint in reflected light |
| Crystal habit | Granular to massive and lamellar exsolutions in hematite or magnetite |
| Twinning | {0001} simple, {1011} lamellar |
| Cleavage | Absent; parting on {0001} and {1011} |
| Fracture | Conchoidal to subconchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5–6 |
| Luster | Metallic to submetallic |
| Streak | Black |
| Diaphaneity | Opaque |
| Specific gravity | 4.70–4.79 |
| Optical properties | Uniaxial (–) |
| Birefringence | Strong; O: pinkish brown, E: dark brown (bireflectance) |
| Other characteristics | Weakly magnetic;Liquidus = 1710°C (peritectic)[2] |
| References | [3][4][5] |
Ilmenite is a titanium-iron(II)oxide mineral with the idealized formulaFeTiO3. It is a weakly magnetic black or steel-gray solid. Ilmenite is the most importantore oftitanium[6] and the main source oftitanium dioxide, which is used as whitepigment in paints, printing inks,[7] fabrics, plastics, paper, sunscreen, food and cosmetics.[8]
Ilmenite is a heavy (specific gravity 4.7), moderately hard (Mohs hardness 5.6 to 6), opaque black mineral with a submetallic luster.[9] It is almost always massive, with thick tabular crystals being quite rare. It shows no discernible cleavage, breaking instead with a conchoidal to uneven fracture.[10]
Ilmenite crystallizes in thetrigonal system with space groupR3.[11][4] The ilmenitecrystal structure consists of an ordered derivative of thecorundum structure; in corundum all cations are identical but in ilmenite Fe2+ and Ti4+ ions occupy alternating layers perpendicular to the trigonal c axis.
Pure ilmenite isparamagnetic (showing only very weak attraction to a magnet), but ilmenite formssolid solutions withhematite that are weaklyferromagnetic and so are noticeably attracted to a magnet. Natural deposits of ilmenite usually contain intergrown or exsolvedmagnetite that also contribute to its ferromagnetism.[9]
Ilmenite is distinguished from hematite by its less intensely black color and duller appearance and its blackstreak, and from magnetite by its weaker magnetism.[10][9]
In 1791,William Gregor discovered a deposit of black sand in a stream that runs through the valley just south of the village ofManaccan (Cornwall), and identified for the first time titanium as one of the constituents of the main mineral in the sand.[12][13][14] Gregor named this mineralmanaccanite.[15] The same mineral was found in theIlmensky Mountains, nearMiass,Russia, and namedilmenite.[10]
Pure ilmenite has the compositionFeTiO3. However, ilmenite most often contains appreciable quantities of magnesium and manganese and up to 6wt% of hematite,Fe2O3, substituting forFeTiO3 in the crystal structure. Thus the complete chemical formula can be expressed as(Fe,Mg,Mn,Ti)O3.[9] Ilmenite forms a solid solution withgeikielite (MgTiO
3) andpyrophanite (MnTiO
3) which are magnesian and manganiferous end-members of the solid solution series.[4]
Although ilmenite is typically close to the idealFeTiO
3 composition, with minor mole percentages of Mn and Mg,[4] the ilmenites ofkimberlites usually contain substantial amounts of geikielite molecules,[16] and in some highly differentiatedfelsic rocks ilmenites may contain significant amounts of pyrophanite molecules.[17]
At temperatures above 950 °C (1,740 °F), there is a complete solid solution between ilmenite and hematite. There is amiscibility gap at lower temperatures, resulting in a coexistence of these two minerals in rocks but no solid solution.[9] This coexistence may result in exsolution lamellae in cooled ilmenites with more iron in the system than can be homogeneously accommodated in the crystal lattice.[18] Ilmenite containing 6 to 13 percentFe2O3 is sometimes described asferrian ilmenite.[19][20]
Ilmenitealters orweathers to form the pseudo-mineralleucoxene, a fine-grained yellowish to grayish or brownish material[9][21] enriched to 70% or more ofTiO2.[20] Leucoxene is an important source of titanium inheavy mineral sands ore deposits.[22]
Ilmenite is a common accessory mineral found inmetamorphic andigneous rocks.[4] It is found in large concentrations inlayered intrusions where it forms as part of acumulate layer within the intrusion. Ilmenite generally occurs in these cumulates together withorthopyroxene[23] or in combination withplagioclase andapatite (nelsonite).[24]
Magnesian ilmenite is formed in kimberlites as part of the MARID association of minerals (mica-amphibole-rutile-ilmenite-diopside) assemblage ofglimmeritexenoliths.[25]Manganiferous ilmenite is found ingranitic rocks[17] and also incarbonatite intrusions where it may also contain anomalously high amounts ofniobium.[26]
Manymafic igneous rocks contain grains of intergrown magnetite and ilmenite, formed by theoxidation ofulvospinel.[19]
Most ilmenite is mined fortitanium dioxide production.[27] Ilmenite and titanium dioxide are used in the production oftitanium metal.[28][29]
Titanium dioxide is most used as a whitepigment, and the major consuming industries for TiO2 pigments are paints and surface coatings, plastics, and paper and paperboard. Per capita consumption of TiO2 in China is about 1.1 kilograms per year, compared with 2.7 kilograms for Western Europe and the United States.[30]
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 TiO2, or more generally "titaniferous slags" if it has a lower TiO2 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.[31]
Ilmenite can be converted into pigment-grade titanium dioxide via either the sulfate process or thechloride process.[32] Ilmenite can also be improved and purified to titanium dioxide in the form of rutile using theBecher process.[33]
Ilmenite ores can also be converted to liquidiron and a titanium-rich slag using a smelting process.[34]
Steelmakers use ilmenite ore as a flux to line theblast furnace hearth refractory.[35]
Ilmenite can be used to produceferrotitanium via analuminothermic reduction.[36]
| Feedstock | TiO 2 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 |
| 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 aplacer 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 asultramafic to mafic layered intrusions oranorthositemassifs. 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.[40]
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.[41]
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 wereRio Tinto Group,Iluka Resources, Exxaro andKenmare Resources, which collectively accounted for more than 60% of the world's supplies.[42]
The world's two largestopen cast ilmenite mines are:
Major mineral sands-based ilmenite mining operations include:
Attractive major potential ilmenite deposits include:
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 andMozambique 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 andUkraine are also big contributors to rutile mining.[31]
China is the biggest producer of titanium dioxide, followed by the United States and Germany. China is also a leader in titanium metal production, but Japan, the Russian Federation, and Kazakhstan have emerged as significant contributors to this field.
Patenting activity related to titanium dioxide production from ilmenite is rapidly increasing.[31] Between 2002 and 2022, there have been 459patent families that describe the production of titanium dioxide from ilmenite, and this number is growing rapidly. The majority of these patents describe pre-treatment processes, such as smelting and magnetic separation, to increase the titanium concentration in low-grade ores, resulting in titanium concentrates or slags. Other patents describe processes for obtaining titanium dioxide, either through a direct hydrometallurgical process or via two industrially exploited processes: the sulfate process and the chloride process.
Acid leaching might be used either as a pre-treatment or as part of a hydrometallurgical process to directly obtain titanium dioxide or synthetic rutile (>90 percent titanium dioxide, TiO2). The sulfate process represents 40 percent of the world's titanium dioxide production and is protected in 23 percent of patent families. The chloride process is only mentioned in 8 percent of patent families, although it provides 60 percent of the worldwide industrial production of titanium dioxide.[31]
Key contributors to patents on the production of titanium dioxide are companies from China, Australia and the United States, reflecting the major contribution of these countries to industrial production. Chinese companiesPangang andLomon Billions Groups are the main contributors and hold diversifiedpatent portfolios covering both pre-treatment and the processes leading to a final product.
In comparison, patenting activity related to titanium metal production from ilmenite remains stable.[31] Between 2002 and 2022, there have been 92 patent families that describe the production of titanium metal from ilmenite, and this number has remained relatively steady. These patents describe the production of titanium metal starting from mineral ores, such as ilmenite, and from titanium dioxide (TiO2) andtitanium tetrachloride (TiCl4), a chemical obtained as an intermediate in the chloride process. The starting materials are purified, if necessary, and then converted to titanium metal through a chemical reduction process using a reducing agent. Processes mainly differ regarding the reducing agent used to transform the starting material into titanium metal: magnesium is the most frequently cited reducing agent and the most exploited in industrial production.
Key players in the field are Japanese companies, in particularToho Titanium andOsaka Titanium Technologies, both focusing on reduction using magnesium. Pangang also contributes to titanium metal production and holds patents describing reduction by molten salt electrolysis.[31]
Ilmenite has been found inlunar samples, particularly in high-Tilunar marebasalts common fromApollo 11 andApollo 17 sites, and on average, constitutes up to 5% of lunar meteorites.[47] Ilmenite has been targeted forISRUwater andoxygen extraction due to a simplistic reduction reaction which occurs with CO and H2 buffers.[48][49][50] TheEuropean Space Agency'sVMMO mission, expected to launch in 2028, intends to map the distribution of ilmenite on the Moon.[51][52]
This article incorporates text from afree content work. Licensed under CC-BY. Text taken fromProduction of titanium and titanium dioxide from ilmenite and related applications, WIPO.
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