Mineral Sands refers to concentrates of minerals usually found in sand deposits, which include titanium minerals ilmenite and rutile.
The mineral zircon is also commonly found in these deposits. Most producers consider zircon to be a co-product of 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 capitalising on titanium feedstocks and zircon. This sector is dominated by close relationships between miners and consumers (predominately titanium dioxide pigments producers).
Not all heavy minerals have economic value. Heavy minerals or Heavy Mineral Concentrate (HMC) are considered valuable because of their properties and prevalence. The exploitable heavy minerals, which are of most interest to Relentless Resources with a density of >3.7 g/cm3 are ilmenite leucoxene, rutile and zircon. It should be noted that Relentless’ HMC contains a 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 contain very high concentrations of heavy minerals – rutile, zircon and ilmenite – averaging 10% to 50%, at a maximum of 100%.
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 of the heavy minerals in the deposit.
Ilmenite and leucoxene
Ilmenite (FeTiO3) is the most common titanium mineral in the Earth’s crust, while leucoxene (Fe.TiO3.TiO2) is a naturally altered form of ilmenite generally used for the same products as ilmenite. Some leucoxene may also be termed tertiary ilmenite.
After ilmenite is released from solid rocks, it is subject to weathering where iron increasingly dissolves, enriching the titanium.
The final ingredient in the weathering process is the mineral mixture leucoxene, which predominantly consists of titanium oxides and, to a lesser degree, iron oxides.
The typical titanium dioxide content for Ilmenite is 48% – 55% with the typical titanium dioxide content for leucoxene 65% - 90%-plus. The colour of leucoxene depends on its titanium dioxide content varying from dark grey to white.
Ilmenite erosion leads to a breakdown of the rock matrix, exposing 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 due to the production of titanium dioxide. Titanium dioxide is 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, enamel, 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% – 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
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 than 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 aluminum, 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 increasingly used in chemical processing plants, oil refineries, water desalination, and heat transfer applications where mildly corrosive seawater is the coolant. Titanium’s cryogenic properties mean 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 it is being used in prosthetic surgery including hip replacements, spinal implants, dentistry and in 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 (ZrSiO4) is used in zirconium compounds, while 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).
|Opacifier in ceramics
Floor and wall tiles, sanitary ware, tableware
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 bbsorption
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