Heavy Mineral Sands
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[edit] Overview
Heavy mineral sands are a class of ore deposit which is an important source of zirconium, titanium, thorium, tungsten, rare earth elements, the industrial minerals diamond, sapphire, garnet, and occasionally precious metals or gemstones.
Heavy mineral sands are placer deposits formed most usually in beach environments by concentration due to the specific gravity of the mineral grains. It is equally likely that some concentrations of heavy minerals (aside from the usual gold placers) exist within streambeds, but most are of a low grade and are relatively small.
[edit] Composition
There are four main heavy minerals that are extracted from mineral sand mining. The first of these is rutile. Rulile is a naturally occurring titanium dioxide. The mineral is commonly red or black in colour, with a specific gravfty of about 4.25 (that’s 4.25 times heavier than water). It is the high quantity of titanium (60%) in rutile that makes it such a desirable heavy mineral for use in a wide range of high technology applications.
Ilmenite is another heavy mineral and like rutile it has a significant titanium content (3 1%). ilmenite is black with a specific gravity that varies from 4.5 to 5.0. Ilmenite can be slightly magnetic.
[edit] General uses
Rutile and Ilmenite
- Many of today’s richest man-made colours owe their high quality to the heavy minerals found in sandy coastal plain. Rutile and Ilmenite are the major raw materials for the world’s paints and dyes.
- Because rutile and ilmenite produce a superior titanium dioxide pigment they are also used to enhance colour in plastics. Some ilmenite is used in the steel industry for furnace linings and foundry moulds due to the mineral’s ability to withstand extreme temperatures.
- The high titanium content in rutile and ilmenite is extracted to produce titanium alloy metals. The titanium is used in hightechnology aerospace design. Primarily used for airframe parts, space-craft and guided missile components, titanium is extremely useful due to its strength-toweight ratio. As a non-reactive metal it is used extensively in making artificial joints in modem surgery.
Zircon
- Zircon is used as the raw material for making refractory bricks and furnace linings due to its melting point of over 2 500 degrees Celsius. It is also used widely in the ceramics industry as a specialty glaze and foundry medium.
- A small percentage of zircon is used in its purest form to make nuclear fuel containers.
Monazite
- Television colour and screen luminescence are dependent upon the production and separation of rare earths from monazite. Video monitors and highefficiency lights all require rare earths for their continued production. The computer, electronic and medical industries all look towards monazite processing as a beginning for future technological developments. [1]
Market Applications for Zircon, Rutile and Ilmenite[2]
[edit] Sources
The source of heavy mineral sands is in a hardrock source within the erosional areas of a river which carries its load of sediment into the ocean, where the sediments are caught up in littoral drift or longshore drift. Rocks are occasionally eroded directly by wave action shed detritus, which is caught up in longshore drift and washed up onto beaches where the lighter minerals are winnowed.
The source rocks which provide the heavy mineral sands determine the composition of the economic minerals. The source of zircon, monazite, rutile, sometimes tungsten, and some ilmenite is usually granite. The source of ilmenite, garnet, sapphire and diamond is ultramafic and mafic rocks, such as kimberlite or basalt. Garnet is also sourced commonly from metamorphic rocks, such as amphibolite schists. Precious metals are sourced from ore deposits hosted within metamorphic rocks.[3]
