Zircon (ZrSiO4) is one of the two core product streams from “mineral sands,” the other being titanium minerals [ilmenite, leucoxene and rutile].
Deposits of mineral sands are formed along ancient coastlines where the heavier minerals have been concentrated by wave and wind action. Most mineral sand deposits are found in unconsolidated fossil shorelines several hundred metres to tens of kilometres – or occasionally hundreds of kilometres – inland from the present coastline. Major deposits are found in Australia and Southern Africa, but also in South and Southeast Asia, China, East and West Africa, Ukraine and in North and South America.
The heavy minerals content of these deposits can range from 0.5% to >20%. Similarly, the zircon content varies from deposit to deposit, ranging from as little as 1% to as much as 50%.
Mining of mineral sands can be by both dry mining and wet (dredge) mining methods. In some countries, mineral sands products, principally titanium minerals, are also recovered from hard rock mining methods.
Dry mining is suitable where deposits are shallow, contain hard bands of rock, or are in a series of unconnected ore bodies.
Dredge mining is best suited to ore reserves below the water table.
Dry mining operations use trucks, excavators, scrapers, loaders or dozer push techniques to recover ore to a mining unit plant. This then conveys the ore to a wet concentrator plant, by slurry pipeline or overland conveyor.
Dredges mine in artificial ponds, pumping ore in slurry form to a floating concentrator.
Wet concentrator plants are designed to produce a high grade of heavy mineral concentrate (about 98 per cent heavy mineral content). The ore is washed through a series of spiral separators that exploit differences in specific gravity to separate the heavy mineral sands from the lighter quartz and clay impurities. The heavy mineral concentrate contains a mix of valuable heavy minerals in different assemblages, as well as residual clays and other non-valuable heavy mineral components and waste.
Following wet concentration, the heavy mineral concentrate is separated into its component minerals (ilmenite, rutile, leucoxene, zircon and monazite) in a dry processing circuit, exploiting the heavy minerals’ different electrostatic, magnetic and density characteristics. Zircon has low magnetic susceptibility and electrical conductivity whereas ilmenite has high magnetic susceptibility and rutile has high electrical conductivity.
Zircon concentrate is dried and cleaned by further electrostatic and gravity separation (to reduce the TiO2 content) to 65% ZrO2 + HfO2, the other principal component being SiO2. Important impurities include Fe2O3, Al2O3 and TiO2.
Zircon is also supplied as a lower-grade concentrate, e.g. from Southeast Asia (Indonesia and Vietnam), with zircon content ranging from 65-85% (average 75%). Most zircon concentrate is supplied to China for further processing.
ZIA has produced a Safety Data Sheet template for Zircon
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