Weathered ilmenite

Ilmenite is more abundant than mtile. Ilmenite world suppHes are estimated to meet the requirements of the Ti02 industry into the twenty-second century. The largest sources of ilmenite are in AustraHa, Canada, South Africa, Russia, and the United States. Large, unexplored sources also exist in China. About 9 million metric tons of ilmenite are mined aimuaHy. Long-term atmospheric effects weather ilmenite into leucoxene [1358-95-8], which contains most of its iron as Fe " . The majority of the world s supply of mtile comes from the beach sands of AustraHa, Florida, India, Bra2H, and South Africa. The total worldwide supply is estimated to be about 50 million metric tons. About 0.5 million tons are mined a year. The supply should last at least until the end of the twenty-first century. 

TiO, is known as leucoxene. Leucoxene is brown to tan, exhibits a rutile X-ray diffraction pattern, is nonmagnetic, less dense than weathered ilmenite, and porcelaneous opaque material. The anisotropy and pleochroism of ilmenite in polished thin section also disappear. 

Major titanium ore deposits are found in Canada (Allard Lake), South Africa (Richards Bay, Namakwa), West Africa (Sierra Leone), Australia (Murray Bassin), Madagascar (Fort Dauphin), Central America (Pluma Hidalgo), South America (Minas Gerais), Norway (Tell-nes), Ukraine, Russia, India, and China in the forms of hard-rock ilmenite, weathered ilmenite, leucoxene, and natural rutile. US domestic deposits are found in California, Florida, Tennessee, and New York. Canada, Australia, South Africa, and Norway are the major producing countries of titania-rich ores and concentrates (USGS 2005). 

TOR minerals (formerly Malaysian Titanium Corp.) Ipoh, Malaysia Benelite 50 Local weathered ilmenite (60-62 wt.% TiO,)... 

In this work, 6 Lac Tio waste rock samples are investigated 3 samples were freshly blasted waste rock and 3 were weathered samples from an old waste rock pile (approximately 25 years old) which underwent significant natural alteration. The ilmenite content varies from approximately 20 to 60 wt% in both... 

The major occurrence of anatase and ilmenite, found in weathered carbonatite bodies, are found in Brazil. Occurrences of rutile and ilmenite in carbonatite-feldspar rocks are found in Mexico and Chile, and in recent years have been subject to extensive investigations. 

Titanium is the ninth most abundant element in the earth s crust, and always occurs in combination with oxygen. The more important titanium minerals are shown in Table 12. Of the natural titanium minerals, only ilmenite, leucoxene, and rutile are of economic importance. Leucoxene is a weathering product of ilmenite. 

Most halloysite appears to be the result of supergene processes and, as noted by Ross and Kerr (1934), leaching by sulphuric acid, produced by the alteration of pyrite, appears to be one of the more common weathering processes. Alunite is commonly associated with halloysite (Ross and Kerr, 1934 Swineford et al., 1954). Sulphuric acid is commonly used to dissolve ilmenite in the manufacture of Ti02 (Willets and Marchett), 1958). It is possible that in nature it serves the same purpose. In the alteration of granitic rocks and pegmatites, feldspar is more likely to alter to halloysite... 

The alteration of all but the most resistant primary minerals occurs in the mid- to upper saprolite zones in addition, less stable secondary minerals such as smectite are also destroyed. Serpentine, magnetite, ilmenite and chlorite are progressively weathered through the zone. Ferromagnesian minerals are the principal hosts for transition metals such as Ni, Co, Cu and Zn in mafic and ultramafic rocks they become leached from the upper horizons and reprecipitate with secondary Fe-Mn oxides in the mid- to lower-saprolite. 

Titanium oxides. These include anatase and rutile (1102), leucoxene (hydrated, amorphous titanium oxide), and ilmenite (FeTi03>, plus zircon (Z1O2) and corundum (AI2O3). Titanium and zirconium are so immobile in soils that members of mineral group are used as indicators of the amount of parent material that has weathered to produce a given volume of soil. 

Spectra for 22 natural ilmenite samples from different deposits show that ilmenite itself is normally deposited with a composition close to the stoichiometry FeTi03 [108]. The weathering products which occur particularly in beach sands contain Fe ions, but are ill defined and of uncertain composition. The degree of weathering can be measured in any given sample from the MSssbauer spectrum. The spectra of lunar ilmenite at various temperatures is discussed on p. 294. 

In both cases, maghemite, a structural polymorph of hematite, is the most common weathering product of magnetite (17, 18). A parallel reaction describing the commonly observed weathering of ilmenite to pseudorutile (19) is... 

The chemical enrichment of titanium dioxide in several oxide minerals. This is particularly important for ilmenite, from which iron is leached during weathering. Other titanium-oxide minerals may be leached of other ions for instance, perovskite may be leached of calcium to form microcrystalline anatase. 

In 2004, nearly 90% of the titanium minerals mined in the world today came either directly from igneous magnetite-ilmenite ore bodies associated with primary anorthosite complexes or secondary placer deposits derived from the weathering of these complexes. 

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