Characteristics of Zirconium

The element zirconium is a very strong but soft, malleable metal. Zirconium is a lustrous silver metal with the chemical symbol Zr. It is highly resistant to corrosion and heat. Zirconium is a ductile metal and as a fine powder is highly flammable. Zirconium is almost always found paired with the element hafnium (Hf). Zirconium is predominantly associated with the minerals zircon and baddeleyite, which are the primary ores of the element (Table 1).

Mineral Name	Chemical Formula	Specific Gravity	Zr %
Zircon	ZrSiO4	4.6-4.7 gm/cc	43.14
Baddeleyite	ZrO2	5.5-6.0 gm/cc	74.03
Kosnarite	KZr2(PO4)3	3.2 gm/cc	36.02
Eudialyte	Na4Ca1.5Ce0.5Fe2+0.6Mn2+0.3Y0.1ZrSi8O22(OH)1.5Cl0.5	2.9 gm/cc	9.19
Hafnon	(Hf,Zr)SiO4	6.97 gm/cc	2.24

Table 1: Minerals containing the element Zirconium

Uses of Zirconium

Zirconium was discovered in 1789. Zirconium is considered a "critical mineral" in domestic metallurgical applications that serve aerospace, defense, and energy technologies (Fortier and others, 2018). There are many uses for zirconium. Due to its non-reactive nature, zirconium may be used in alloys for pipes and fittings in corrosive environments. Zirconium is also used as an opacifier in high temperature ceramics, as an abrasive, in lamp filaments, catalytic converters, surgical instruments, and furnace bricks. It can be used to harden steel and shape molten metals as a mould. Zirconium is also useful in the nuclear-reactor industry as a corrosion-resistant and low-neutron absorbing casing for fuel rods. Scientists also use the mineral zircon for geochronology.  

Zirconium Geology

Zirconium is often found with the elements hafnium and titanium in igneous and metamorphic rocks. Zirconium originates from the cooling and crystallization of magma as it mixes with the surrounding rock in the Earth's crust, where zirconium is common. Igneous rock forming from deep mantle-sourced magma may have a greater concentration of zirconium, as the shallow mantle is relatively depleted in the element. Because zirconium-containing minerals, such as zircon, are highly resistant to weathering, they eventually erode out of host rocks and may accumulate elsewhere as heavy mineral sand placer deposits. Economic deposits of heavy minerals may be found in modern sediment accumulations as well as in ancient beach deposits that may be far inland from today's shorelines.

Mineral System	Deposit Type	Geologic Provinces
Placer	Paleo-placer in Pliocene sediments (heavy mineral sands)	Coastal Plain

Table 2: Prospective zirconium mineral systems, deposit types (Hofstra and Kreiner, 2020), and geologic provinces in Virginia

Zirconium in Industry

Although zirconium is relatively abundant globally, the element is typically distributed in low concentrations. The U.S. does not maintain a supply of zirconium in the National Defense Stockpile, and is approximately 50 percent reliant on zirconium ore and concentrate imports from South Africa, Senegal, and Australia. The United States also exports zirconium. In the United States, zirconium is mined in Florida and Georgia. Concerns related to mining for zirconium include erosion from surface mining, disruption of the surrounding ecosystem, and inhalation of zirconium dust during industrial processing.

In Virginia, Zircon is sourced from deposits of heavy mineral sands. Zircon, in addition to ilmenite and rutile, occur as paleoplacer deposits along an ancient coastline that is now exposed primarily in Dinwiddie and Greensville Counties. The heavy minerals were naturally concentrated by wind and wave action in beach and sand dunes about 3 to 4 million years ago during the Pliocene Epoch, when the shoreline of the Atlantic Ocean was at a higher elevation (near Richmond).

Hanover County

Several historic prospects for zirconium (from zircon) have been reported near the town of Ashland in the Hanover County. Samples of sandstone rich with ilmenite and zircon were identified in 1910 along the contact of the Petersburg Granite and overlying Calvert Formation sands. Although samples contain approximately 30 percent zircon by weight, the area was not industrially mined (Watson and Hess 1913).

Dinwiddie and Greensville Counties

In eastern Dinwiddie and Greensville Counties, economic heavy mineral sands containing zirconium occur as paleoplacer deposits along a now exposed ancient coastline. The heavy minerals were naturally concentrated in Pliocene-age shoreline beach and dune sands by wind and wave action. The key heavy minerals in these deposits include ilmenite, rutile, zircon, and leucoxene (mixture of altered titanium bearing minerals). In 1996, mining and processing of the heavy mineral sands began from the Old Hickory deposit. A second mine (Brink) was permitted about 19 miles to the south in Greensville County in 2008. At both sites, heavy mineral sands are mined by excavator and then processed to separate each heavy mineral (ilmenite, leucoxene, rutile, and zircon) by weight and magnetism. In 2017, Iluka Resources Ltd. suspended operations, but continues to hold mining leases in these areas.

The Pliocene heavy mineral sand deposits are considered an onshore analog for what may represent an undiscovered economic resource contained in sand shoals that have formed on Virginia's outer continental shelf. In an investigation that included analysis of 390 sediment samples from offshore vibracore and grab samples, Berquist (1990) reported concentrations of one or more economic minerals that were equal to or greater than the economic cut-off grades for onshore deposits. The Virginia Division of Geology and Mineral Resources is conducting investigations to assess the offshore resource potential.