What is zircon sand?
Zircon, also known as zircon silicate (ZrSiO4), is found in ancient mineral sand deposits. In the form of crystal sands, zircon is typically brown, but could also vary from colourless to yellow-golden, pink and red to blue and green.
Zircon is one of the two core product streams from ‘mineral sands’, the other being titanium minerals (ilmenite, leucoxene and rutile).
The majority of zircon sand is mined in Australia and the African continent. Current annual global production is in excess of one million tonnes. Almost half of the zircon produced globally is consumed by China, with other significant consuming regions including Europe, North America, Asia-Pacific and India.
The main use of zircon sand is its conversion into flour, opacifier, fused zirconia, zirconium chemicals, chemical zirconia and zirconium metal. Zircon sand is directly used in foundry applications and refractories and other minor applications.
Where is zircon found?
Deposits of mineral sands are formed along ancient coastlines where the heavier minerals were 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 mineral content of these sand 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%.
How is zircon mined?
Mineral sands can be extracted using two primary methods: dry mining and wet (dredge) mining. In some countries, hard rock mining methods are also utilized to recover mineral sands products, particularly titanium minerals.
Dry mining is typically employed in situations where deposits are shallow, contain hard rock bands or are situated in a series of unconnected ore bodies. This approach involves the use of trucks, excavators, scrapers, loaders or dozer push techniques to extract ore which is then conveyed to a mining unit plant for further processing. The ore is subsequently transported to a wet concentrator plant either by a slurry pipeline or overland conveyor.
Dredge mining is more suitable for ore reserves that lie below the water table. Dredges operate within man-made ponds, employing pumping mechanisms to extract ore in slurry form and deliver it to a floating concentrator.
Wet concentrator plants are designed to produce highly concentrated heavy minerals, typically with around 98% heavy mineral content. After washing the ore through a series of spiral separators to remove lighter quartz and clay impurities, heavy mineral sands are separated from the remaining material. The heavy mineral concentrate obtained contains a mix of valuable heavy minerals as well as residual clays and other non-valuable heavy mineral components and waste. Following wet concentration, the heavy mineral concentrate is subjected to a dry processing circuit to separate its component minerals (ilmenite, rutile, leucoxene, zircon, and monazite) based on their differing electrostatic, magnetic and density characteristics. Zircon, for example, has low magnetic susceptibility and electrical conductivity, whereas ilmenite has high magnetic susceptibility and rutile has high electrical conductivity.
Zircon concentrate is subsequently dried and cleaned via further electrostatic and gravity separation procedures in order to reduce the percentage of TiO2 to 65% ZrO2 + HfO2, with SiO2 as a principal accompanying component. Notable impurities in zircon concentrate include Fe2O3, Al2O3 and TiO2.
Zircon concentrate is also available in lower-grade forms, sourced mainly from Southeast Asia (Indonesia and Vietnam), with a zircon content range between 65% to 85% (average 75%). The majority of zircon concentrate supply is delivered to China for further processing.