The term ‘mineral sands’ refers to concentrates of minerals commonly found in sand deposits, which include titanium minerals ilmenite and rutile. The other mineral of significance commonly found in these deposits is zircon, which most producers consider as a co-product of the titanium mineral products. Alluvial deposits have been found in Australia, southern, western and eastern Africa, Sri Lanka, Madagascar, USA, South East Asia, South America and Ukraine. These deposits are the world’s main sources of ilmenite, rutile and zircon with only a small number of mining companies or groups being involved in capitalizing on titanium feedstocks and zircon. This sector is dominated by close relationships between miners and consumers (predominately titanium dioxide pigment producers).
Of the numerous heavy minerals, only a few have economic significance due to their properties and prevalence. These are commonly referred to as valuable heavy minerals or Heavy Mineral Concentrate. The mostly exploitable heavy minerals with a density of >3.7 g/cm 3 are ilmenite leucoxene, rutile and zircon, and these are of the greatest interest to Relentless Resources. It should be noted that Relentless’ HMC contains a very low percentage of monazite.
Figure 1, 2 and 3 (Left to Right) - Ilmenite, Rutile, Zircon products
Heavy Mineral Deposits
Globally, significantly large deposits of heavy minerals such as ilmenite, rutile and zircon form so-called beach placers or strandline deposits. Strandlines are formed in such a way, that they have very high concentrations averaging 10% to 50% heavy minerals, at a maximum of 100%. They mainly form concentrations of heavy minerals of economic interest (e.g. rutile, zircon, ilmenite). Coastal dunes are formed by the blow-out of strandlines. Due to the preferred incorporation of light minerals, dunes are generally less rich in heavy minerals than the adjacent beach sands and these typically occur in the same basinal vicinity as strandlines. The mineral sands industry primarily supplies raw titanium materials for the manufacture of titanium dioxide pigments and titanium metal. The other economically significant mineral in heavy mineral deposits is zircon, typically comprising 10%-15% of the mineral assemblage.
Ilmenite and Leucoxene
Ilmenite (FeTiO3) is the most common titanium mineral in the Earth’s crust. Leucoxene (Fe.TiO3.TiO2) is a naturally altered form of ilmenite and is generally used for the same products as ilmenite. After the ilmenite is released from solid rocks, it is subject to weathering. Iron increasingly dissolves, and titanium becomes relatively enriched. The final member in the weathering process is the mineral mixture leucoxene, predominantly consisting of titanium oxides and, to a far lesser degree, iron oxides. In pr actice, the distinction between altered ilmenite and leucoxene is arbitrary and commercially-based. Some leucoxene may also be termed tertiary ilmenite.
The typical titanium dioxide content for Ilmenite is 48% to 55% and the typical titanium dioxide content for Leucoxene is 65% to 90+%. The inherent colour of leucoxene directly depends on its titanium dioxide content varying from dark grey (56 -63% TiO2) to white (95-100% TiO2).
Ilmenite erosion leads to breakdown of the rock matrix and the exposure of the ilmenite. Due to its stability against physical and, to a lesser degree, chemical weathering, ilmenite is relatively stable in the weathered environment, allowing it to concentrate and form large strandline deposits.
The significance of ilmenite as the most important, rock-forming titanium mineral, is not due to the extraction of titanium metal but the production of titanium dioxide. Titanium dioxide is by far the most significant white pigment in the world, and is used, amongst other things, in paints and varnishes, printing inks, plastics, rubber, linoleum, artificial fibres, paper, glass, en amel, and ceramics (see figure below). With only a few exceptions, the white materials in almost all applications worldwide owe their “colour” to titanium dioxide pigments.
Use in pigment accounts for approximately 80% to 90% of total global demand for titanium dioxide feedstocks. Titanium metal and welding flux cord wire jointly account for the remaining 10% to 20% of demand.
Titanium Dioxide characteristics and uses
Paints and coatings, plastics / paper
|Opaque, White and Bright
High refractive index (refracts * reflects white light)
Absorbs UV light energy (transfers to heat) – prevents fading, peeling and cracking
Safe for use in foods, cosmetics and pharmaceuticals
|Welding Flux Agent
Ship building and fabrication
Important constituent of welding to shape, hold and protect the weld pool from atmospheric conditions
Dye-sensitive solar cells, arsenic removal in water treatment, cancer treatment and noise absorption
|Nano Particles |
Significant research into nanotechnology shows promising new applications for titanium dioxide
Rutile - Titanium Metal
Rutile (93%+ TiO2) typically occurs in much smaller proportions to ilmenite in strandline deposits and has a higher titanium dioxide content than ilmenite or leucoxene. Rutile is used as a high-grade top-up in times of increased plant utilisation, and in the production of titanium metal. Titanium metal is 45% per cent lighter than steel, twice as strong as aluminium, and can be machined with the same equipment as stainless steel. These characteristics, combined with the low thermal expansion coefficient and high melting point (1670 ° C), have enabled titanium and its alloys to find important applications in the aerospace and defence industries (see figure below). Under atmospheric conditions the metal is resistant to corrosion; and it is unaffected by strong alkalis, chlorides, sulphides or nitric acid. These properties mean that titanium is now being increasingly used in chemical processing plants, oil refineries, water desalination, and heat transfer applications where mildly corrosive seawater is the coolant. Titanium’s good cryogenic properties mean that it can be used in tanks for shipping liquid nitrogen, hydrogen or helium.
Aircraft engines & airframes, military equipment, chemical processing and desalination plants, medical and sporting equipment
|High strength to weight ratio
Strong as steel but 45% lighter, twice the strength of aluminium which provides an important fuel efficiency benefit in aerospace applications
Forms and inert protective oxide coating self-repairs when mechanically damaged
Titanium metal is increasingly used in advanced engineering applications, spectacle frames, jewellery, bicycle frames and sporting goods. Its general inertness means that it is finding use in prosthetic surgery, such as hip replacements, spinal implants, dentistry and in heart pacemakers.
Figure 4: Titanium metal used in implants and prostheticsIncreasing use is being made of 3-D printing to produce many customised applications using titanium powder (see Figure 4).
Figure 5: Titanium Metal Used in 3D Printing
Over 95% of zircon is used in various zirconium compounds, whilst less than 5% of recovered zircon is used in the production of metal. Its hardness, high melting point and low expansion coefficient when heated, means that standard grade zircon is particularly suited as foundry sand and as an abrasive. Almost half of the zircon produced is used in ceramics applications due to its ability to scatter and reflect light. The surface layer of most tiles, bathware and crockery obtain their glazed finish, durability and resistance to discolouration, from zircon being melted into their surfaces (see figure below)
Zircon Characteristics and Uses
|Opacifier in Ceramics
Floor and Wall tiles, sanitary ware, table ware
High refractive index (Zircon refracts and reflects white light well)
Water, chemical and abrasion resistance of glazes due to hardness of zircon
|Refractory and Foundry
Steel / Glass production, casting of jet turbine engines
Low thermal expansion coefficient, high thermal conductivity due to hardness of zircon
Against molten metals
Nuclear reactor cores / rod heat exchanges
|Low Thermal Neutron Absorption
Increases nuclear reactor efficiency
|Zirconia & Zirconium Based Chemicals
Refractions, pigments, abrasives, electronics, catalysts, fibre optics
Compound derivatives of Zircon suitable for diverse industrial and chemical applications