Mineral commodity report 19 - beryllium, gallium, lithium, magnesium, uranium a

Mineral Commodity Report 19 - Beryllium, Gallium,
Lithium, Magnesium, Uranium and Zirconium
by Tony Christie and Bob Brathwaite
thermal conductivity, is nonmagnetic and has a high Institute of Geological and Nuclear Sciences Ltd permeability to X-rays. Its modulus of elasticity is aboutone third greater than that of steel and, although brittle, it Beryllium
has a high strength per unit weight. It resists attack byconcentrated nitric acid, and tarnishes only slightly in air, Discovery and origin of names
becoming covered with a thin layer of oxide.
Precious stone varieties of the beryllium mineral beryl have The properties of some beryllium minerals are listed in Table been known for six thousand years. When polished, beryl 1. The main beryllium mineral, beryl, occurs as hexagonal served as an eyeglass, for example, it was used by Nero crystals that may grow to a large size, up to 0.5-0.9 m across whilst observing Rome on fire in 64 A.D. Beryllium was and several metres long. The largest beryl crystal yet discovered as an oxide, now known as beryllia, in beryl discovered, from the Picuí deposit in Paraiba, Brazil, and in emeralds in 1798 by the French chemist Louis weighed 200 t. Emerald is a transparent, intensely green Vauquelin. The pure metal was isolated in 1828 independently by Friedrich Wöhler in Germany andAntonine Bussy in France.
Formation
Beryllium was first called glucinum from the Greek glykys, Beryl is found in coarsely crystalline pegmatite dikes that for sweet, because the soluble compounds are sweet-tasting.
occur peripheral to some granitic intrusions and represent However, Wöhler established the name beryllium, after the the late stage crystallisation of residual fluids. The chief mineral beryl, named from the Greek beryllos.
pegmatites are composed of quartz, sodic plagioclase andmicrocline with or without spodumene, muscovite or Major ores and minerals
lepidolite. Such pegmatites are common in the ancient Beryllium does not occur free in nature, but is an essential continental shield areas of Canada, Australia and Africa; constituent in about 40 minerals and may also be present in the USA, they are found in the southern Appalachians, in some 50 others, including plagioclase, micas and clays.
New England and the Black Hills of South Dakota.
This widespread occurrence results from its ability to replace Beryllium is also found in replacement deposits including silicon in minerals. Beryl and bertrandite are the principal epithermal mantos in tuffs, tactite or emerald-bearing ore minerals (Table 1), although deposits of chrysoberyl schists. An important example is Spor Mountain, Utah, and phenakite may become economically significant in the USA, where bertrandite mineralisation is associated with future. Rare gem forms of beryl include green emerald, epithermal alteration of rhyolitic, water-laid tuffs of Pliocene blue aquamarine, pink morganite and colourless goshenite.
age, particularly in parts of the tuff containing carbonatepebbles eroded from Paleozoic limestone and dolomite. The Properties
main alteration products are smectite, quartz, fluorite and Beryllium is one of the alkaline-earth metals of Group IIa adularia. Grades are typically less than 0.5% Be. The of the periodic table. It is a steel grey coloured metallic chrysoberyl deposits of the Seward Peninsula, Alaska, are element, one of the lightest of all metals, and has one of the replacement bodies in limestone and consist of very fine highest melting points of the light metals. It has excellent grained fluorite, diaspore and chrysoberyl.
Table 1: Properties of some beryllium minerals.
Beryllium is recovered from hydrothermal-pneumatolytic appliances, and instrumentation and control systems. A skarn and greisens that also contain tin, fluorite and/or rapidly expanding use is in oil and gas drilling equipment.
tungsten. Skarns may contain up to 0.7% BeO in the Beryllium alloys are also used in precision moulds for the mineral helvite. Beryl and bertrandite are also found plastics industry, and in consumer leisure markets they are associated with fluorite in mica quartz greisen near a granitic used in high quality golf club heads, as well as in consumer intrusion in Park County, Colorado. Phenakite and electronics such as stereo systems, VCRs, portable bertrandite occur with scheelite, fluorite and pyrite in White telephones, miniature radios and video cameras.
Pine County, Nevada. Other beryllium deposits are in Sea Beryllium oxide (beryllia) is used in the manufacture of high Lake, Labrador, Canada, as barylite; and in Coahuila, temperature ceramics and high-quality electrical porcelains, in microwave tube parts (e.g. cathode supports, envelopes, Nepheline syenite and other nepheline-bearing rocks may spacers, helix supports, collector isolators, heat sinks and contain up to 0.1% BeO, and at the rare metals deposit at windows), in solid state electronic devices, in bores or Thor Lake, near Yellowknife in the Northwest Territories plasma envelopes for gas lasers, and as a slurry for coating of Canada, five deposits have been identified as a large resource of tantalum-niobium, rare earths, zirconium,gallium and beryllium. They are contained within a large Beryllium metal is used in nuclear reactors as a moderator gabbroic to syenitic and granitic body of alkaline affinity to lessen the speed of fission neutrons and as a reflector to with resources of 1.6 Mt grading 0.85% BeO (see rare earths reduce leakage of neutrons from the reactor core.
mineral commodity report; Christie and Brathwaite, 1998a).
Because beryllium is relatively transparent to X-rays it is used Beryllium has been recognised as concentrating in coals, in ultra thin sheet or foil form as window material in x-ray with an average of 46 ppm in coal ash.
tubes for transmission of rays and to filter out electrons.
Beryllium is mostly used in the production of special alloys Prices for beryl (10% BeO) in August 1999 were US$75- (75%), and to a lesser extent as beryllium oxide (15%), 80/short ton BeO cif (Mining Journal, August 20, 1999).
World production and consumption
Beryllium is added to alloys to increase heat resistance, Total world production of beryllium in 1998 was estimated corrosion resistance, hardness, insulating properties and at 330 t of contained beryllium. Beryl was mined at better casting qualities. Beryllium-copper alloys, containing operations in China (55 t of contained Be in 1998), Russia about 2% Be, are the most important, although beryllium- (40 t), Kazakhstan (4 t) and Brazil. Sporadic output is aluminium alloys, with about 65% Be and 31% Al, are occasionally recorded in Zimbabwe, Zambia, Madagascar, becoming increasingly used in aerospace, electronics, Argentina and Portugal. Bertrandite is produced from Spor telecommunications, consumer products and robotics.
Mountain area of Utah, with an output of about 230 t of Beryllium-copper alloys are manufactured into springs, connectors, and switches for use in applications inautomotive, aerospace, radar and telecommunications World resources of contained beryllium have been estimated industries, and in factory automation, computers, home by the US Bureau of Mines to exceed 1.3 Mt, with 35% in Brazil, 16% in India, 15% in the Commonwealth ofIndependent States (CIS), and 7-8% each in the USA andArgentina. In China, the largest resources are found inInner Mongolia.
Ore processing, smelting and refining
Two processes are used to extract beryllium oxide or
hydroxide from beryl ore. In the first the beryllium is selectively
extracted by roasting beryl with sodium fluorosilicate at
700-750oC and leaching the product with water to extract
soluble beryllium fluorides (Copaux process). Beryllium is
recovered from the fluoride leach liquors by precipitation
as the hydroxide at pH 12. In the second method, the fuse-
quench process, beryl is melted in an electric furnace at
1600-1650oC and quenched to a glass by pouring into water.
The glass is devitrified by heating to 900-950oC to make it
more reactive with dilute acid. The devitrified glass is
broken down by heating with sulphuric acid.
Bertrandite and barylite ores are less refractory than beryland can generally be treated with moderately strong acidto extract the beryllium directly. At Spor Mountain thebertrandite ore is wet-milled and the slurry is leached withsulphuric acid at temperatures near the boiling point. Aleach liquor containing BeSO separated from the solids is concentrated using solvent extraction. The next stage formsberyllium carbonate, 2BeCO .Be(OH) , which precipitates out on heating. Further heating forms Be(OH) . After filtering, this product is shipped to the company’s Elmore, Figure 1: Location of beryllium deposits in New Zealand.
Ohio, plant for processing into metal, beryllium-copperalloy or beryllia ceramic products.
Future trends
New Zealand occurrence and resources
Defense industry applications of beryllium have declined, Beryl occurs in pegmatites near Charleston on the West whereas there is an increasing use of beryllium alloys and Coast, and on the north shore of Paterson Inlet, Stewart ceramics in the telecommunications and electronics Island (Fig. 1). The pegmatites near Charleston are hosted industries, and of beryllium-copper alloys in the automotive in banded granitic Constant Gneiss and contain coarse industry. The increased use of beryllium-aluminium alloys grained quartz, feldspar, muscovite and biotite. Beryl occurs compared with beryllium-copper alloys is expected to as columnar, pale green to colourless crystals up to 125 increase the demand of beryllium because of the higher mm across and containing 12.82% BeO (Hutton and Seelye, content of beryllium in beryllium-aluminium alloys.
1945; Officers of New Zealand Geological Survey, 1970a).
At Paterson Inlet, beryl occurs as fine grained crystals in association with abundant tourmaline (McKay, 1890).
Hutton and Seelye (1945) referred to the existence of beryl Discovery and origin of names
at Dusky Sound, but gave no specific location or reference.
Gallium was discovered in 1875 by Paul-Émile de In the Canaan Valley, Pikikiruna range, quartz veins Boisbaudran, who observed its principal spectral lines while associated with Separation Point Granite contain rare, blue examining material separated from sphalerite. A year later and colourless beryl crystals, and scheelite (Williams et al., he isolated the element in its metallic state by electrolysis 1959). The beryl is mostly very fine grained, but a few of a solution of the hydroxide in KOH. He found that its crystals up to 8 mm in size are present. Beryl is also present properties coincided with those Dimitry Mendeleyev had in nearby stream alluvium (Officers of New Zealand predicted a few years earlier for eka-aluminium, the then undiscovered element lying between aluminium and indiumin his periodic table. Boisbaudran named the new element Analyses from the ilmenite-bearing beach sand on the West in honour of his homeland Gaul, derived from the Latin Coast, during prospecting in the 1970s, showed traces of Gallia, France, and also from the Latin, gallus, a translation beryl. In the Birchfield licence, it comprised 0.01% of the heavy mineral fraction, and 0.02% at Hokitika(Zuckerman, 1972; Painter, 1973). Hutton (1950) noted Major ores and minerals
that some West Coast dredge concentrates contained rare Gallium does not occur free in nature or as a major grains of gadolinite that were probably eroded from constituent of any minerals, apart from gallite (CuGaS ), but it is present in trace quantities in most aluminosilicate Cohen et al. (1967) noted high background concentrations minerals, particularly bauxite, some clays (e.g. kaolin and of beryllium in the Hawks Crag Breccia of the lower Buller diaspore), sphalerite, pyrite and magnetite, as well as in Properties
was probably present in kaolinite, substituting for Gallium is a metallic element in Group IIIa of the periodic aluminium. He noted that mud samples from Champagne table, and is one of the few metals that is liquid at or near Pool (Waiotapu), Lagoon Corner (Rotokawa) and Lake room temperature. Further, it remains in the liquid state Rotoa-Tamaheke (Rotorua), that have high gallium over a wider range of temperatures than any other element concentrations (>70 ppm), also contain high concentrations (30oC to 2403oC). It is blue-grey in colour as a solid and of antimony (400->5000 ppm) and arsenic (800->10,000 silvery as a liquid. The solid metal is soft and exhibits a ppm). These two elements form colloids that are efficient conchoidal fracture similar to glass. Gallium wets glass or scavengers of metals. Co-precipitation of gallium with these porcelain, and forms a brilliant mirror when it is painted colloids is a possible deposition mechanism.
on glass. Somewhat similar to aluminium chemically,gallium slowly oxidises in moist air until a protective film Future trends
forms, and it is attacked only slowly by acids. Gallium Gallium could be recovered from coal ash and coal, and extracted from polymetallic ores by leaching. Demand mayincrease for use in gallium-based electronic devices, in Formation
equipment converting solar energy to electricity, and, There are no concentrated deposits of gallium, instead possibly, in commercial microwave applications.
gallium is produced as a byproduct of aluminiumproduction from bauxite, and less commonly from zinc production from sphalerite. The occurrences of bauxiteand sphalerite ores are described in the aluminium and lead- Discovery and origin of names
zinc mineral commodity reports respectively (Christie et The lithium-containing minerals, petalite and spodumene, al., 1993; Christie and Brathwaite, 1995a). Gallium is more were discovered by Jose de Andrada between 1790 and abundant in bauxites derived from granitic and alkalic 1800 in Sweden. Lithium was discovered in 1817 by Johann rocks, and the Ga:Al ratio increases with weathering Arfvedson in Sweden during an analysis of petalite ore.
intensity. In zinc ores, the gallium contents are higher in Humphry Davy and Brandé independently isolated the replacement deposits formed at lower temperatures. The metal in 1818 by electrolysis of lithium oxide. The name Tri-State and Upper Mississippi Valley districts have been lithium is from the Greek lithos “stone”, because it was The Tsumeb deposit in Namibia, a pipe-like replacement Major ores and minerals
body of copper-lead-zinc sulphides, is unique in itsproduction of a germanite-renierite concentrate, which has Lithium is not found free in nature, but it occurs in small been the dominant source for European refining of gallium amounts in nearly all igneous rocks and in the waters of and germanium. The deposit has been the source for most many mineral springs. Spodumene, lepidolite, petalite and of the other reported gallium minerals from oxidised ores.
Uses
Approximately 95% of gallium consumed is used in the
electronics industry, mainly in semiconductors for transistors,
rectifiers, light sources, lasers and photocells. Minor quantities
have been used in thermometers, low-melting solders, as a
heat-transfer fluid, in arc lamps, batteries, vanadium-
gallium superconductors, and in catalyst mixtures.
Ore processing, smelting and refining
Bauxite ore is dissolved in sodium hydroxide solution,
producing a gallium-bearing sodium aluminate solution,
with recovery accomplished by fractional carbonation and
electrolysis.
Gallium is also recovered in smelting sphalerite. Galliumis reduced with the zinc metal, which is distilled off. Thegallium is recovered from the flue dust and from the residuesof the zinc purification process. The material is dissolvedin aqueous hydrochloric acid and then gallium is separatedby solvent extraction. The gallium is recovered from theorganic solvent, further purified, and then reduced to themetal.
New Zealand occurrence
Gallium is present in muds and sinters of geothermal fields
of the Taupo Volcanic Zone. Crump (1994) reported
gallium concentrations ranging between 8 and 144 ppm in
48 surface samples from 11 major geothermal fields (Fig.
2). Crump considered that in the mud samples, the gallium
Figure 2: Location of lithium and gallium deposits in New Zealand.
amblygonite (Table 2) are the most common of the 40 or and the Taupo Volcanic Zone, New Zealand. Other waters may be enriched in lithium, for examples oilfield brines inthe Paradox basin, Utah, and in the Smackover Formation Properties
in Arkansas and Texas. Brines may be concentrated by Lithium is the first element in Group Ia of the periodic table, evaporation in desert regions. Examples include Clayton the alkali metals. It is white, with a silver lustre, and has a Valley, Esmeralda County, Nevada; Searles Lake, California; hardness of 0.6 (softer than lead). It is the lightest solid Great Salt lake, Utah; Salar de Atacama, Chile; Salar de element, with a density only about half that of water. It is Hombre Muerto, Argentina; and Salar de Uyuni, Bolivia.
highly reactive and resembles sodium in its chemicalbehaviour. It reacts with water (but not as vigorously as sodium), the non-metals, inert gases excepted, most of the Lithium minerals such as spodumene are used in ceramics, metalloids, and many of the metals. It tarnishes glass, frits and glazes. Lithium metal is used in batteries, instantaneously and corrodes rapidly upon exposure to air; nuclear fusion power plants, vitamin-C synthesis, and light- when it is stored it must be immersed in a liquid such as weight high-strength alloys. The metal is used as a naphtha. Lithium imparts a crimson colour to a flame, but deoxidizer and to remove unwanted gases during the when the metal burns strongly the flame is a dazzling white.
manufacture of non-ferrous castings. Lithium vapour isused to prevent carbon dioxide and oxygen from forming The properties of some lithium minerals are listed in Table 2.
scale in furnaces in heat-treating steel. The major industrial Formation
use of lithium is in the form of lithium stearate as a thickenerfor lubricating greases. Lithium carbonate is used in Lithium is recovered from brines and from minerals in ceramics, pharmaceuticals, and aluminium production, and granite pegmatites, and in the future may also be recovered as a fluxing agent and catalyst; lithium hydroxide is used in alkaline storage batteries and to make lithium salts, Lithium-bearing granite pegmatites are found as dikes greases and soaps; lithium chloride is used in lithium metal peripheral to granite intrusions, and were formed by production, fluxing, air conditioning and dry batteries; crystallisation of late stage residual fluids. Lithium occurs lithium fluoride has various uses in ceramics, optics and in a paragenetic range from early-stage minerals like iron- glazes; lithium bromide is a drying agent and adsorbent in rich spodumene through intermediate stages (spodumene, refrigeration; lithium hydride is used to inflate lifeboats, petalite, lepidolite and amblygonite) to low temperature and its heavy hydrogen (deuterium) equivalent is used in hydrothermal alteration products such as eucryptite, bikitaite making the hydrogen bomb; butyl-lithium is used in and cookeite. Examples occur in King Mountain, North pharmaceuticals, polymerisation and organic synthesis; and Carolina; Black Hills of South Dakota; Bernic Lake, Manitoba lithium-copper and lithium-silver alloys are used as self- (Tanco pegmatite); Aracuai, Minas Gerais, Brazil; Altai fluxing brazing alloys. Lithium is also an essential source Mountains, China; Chita region, Russia; Bikita mine in for the tritium required in various thermonuclear (fusion) Zimbabwe (Bikita pegmatite); Karibib, Namibia (Rubicon power reactor designs such as the Tokamak where it also and Helicon pegmatites); “tin mineral province” in Zaire; serves as a neutron absorber and heat exchanger.
and Greenbushes pegmatite field, Western Australia.
Lithium is increasingly used in lighting, fibreglass, lead Lithium-rich brines are found in areas of volcanic activity crystal and glaze products, and as a substitute for such as Imperial Valley, California. Reykjanes Field, Iceland, environmentally unfriendly elements such as fluorine.
Table 2: Properties of some lithium minerals.
The lithium was extracted by dosing the brine with sodium Prices for lithium minerals in August 1999 were US$250/t aluminate to form lithium aluminate, which was adsorbed freight on board (fob) for petalite (4.2% Li O), US$385- on aluminium hydroxide. About 10% of the sodium and 395/t fob for spodumene (>7.25% Li O), and US$1.00- potassium present in the water follow the lithium presenting 2.00/lb for lithium carbonate (Industrial Minerals, August difficulties in further refining and upgrading the lithium 1999; Mining Journal, August 20, 1999).
into a marketable form. The trials were abandoned asuneconomic at the time.
World production and consumption
Future trends
Lithium is presently being recovered from brines of SearlesLake, in California, and from those in Nevada. Pegmatite An increase in the use of lithium materials is expected in deposits are mined in Australia, Canada, Zimbabwe, China, glassware, rechargeable lithium batteries, fuel cells and other energy-related applications. There is potential forsubstantial use in the structural metal field, particularly in World lithium resources are about 2,200 t, 34% are in pegmatites and 66% in brines. Of the pegmatite segment,33% is spodumene and 1% petalite.
Magnesium
Ore processing
Discovery and origin of names
Lithium ores are concentrated from 1-3% Li O to 4-6% Compounds of magnesium have long been known. A small Li O by heavy media separation using dense, nonaqueous implement made of magnesite was found along with ancient liquids, and by froth flotation. The silicate ores are then Babylonian glassware and the use of gypsum for mortar chemically cleaved by acid or alkaline processes.
was recorded in the first century AD. Black recognised In the acid process, spodumene ore is heated in a kiln at a magnesium as an element in 1755. It was first isolated by temperature of about 1100oC. After calcining, the ore is the British chemist Sir Humphry Davy in 1808, who mixed with sulphuric acid and roasted at 250oC and then evaporated the mercury from a magnesium amalgam made extracted with water to yield a solution of lithium sulphate.
by electrolysing a mixture of moist magnesia and mercuric Lithium carbonate is recovered by addition of sodium oxide. It was prepared in coherent form by Bussy in 1831.
carbonate to the solution after pH adjustment, purification Magnesium is named after ancient Magnesia, a district in and evaporation. The carbonate is converted to the chloride Thessaly, Greece. During antiquity, the term magnesia was applied to the soft white mineral steatite, also known as In the alkaline process, spodumene or lepidolite ores are soapstone or talc. Epsom salts were named from the spring ground and calcined with limestone at 900-1000oC. The discovered at Epsom, England in 1618. N. Grew studied resulting clinker is crushed, milled and extracted with water the brine and isolated solid Epsom salt in 1695. Talc is to yield lithium hydroxide which is converted to the chloride from the Arabic talq and was first used by Jahiz of Bassora in 1869. The term steatite, introduced by Pliny the Elder,is from the Greek word steatos meaning fat.
Lithium metal is prepared by the electrolysis of a fusedmixture of lithium chloride and potassium chloride in a Major ores and minerals
cell at a temperature of about 400oC.
Magnesium is the eighth most abundant element in the Lithium is recovered from the brines of Searles Lake, earth’s crust (about 2%). It does not occur in nature as an California (<100 ppm Li) by concentration and precipitation element, but is found in over 60 minerals such as magnesite, as dilithium sodium phosphate. The mixed phosphate is dolomite, brucite, chrysolite and talc (Table 3). Garnierite then converted to lithium carbonate, which is the final (Ni,Mg)SiO .nH O is an ore of nickel. Spinel is a lithium containing product. Brines from Clayton Valley, metamorphic magnesium mineral (MgAl O ) sometimes Nevada, contain about 200 ppm Li and low concentrations used as a gem. Magnesium is also widely distributed in of alkaline earths, simplifying recovery. The lithium is salt forms, such as magnesium chloride, in sea water, recovered after the brine is concentrated by solar saline-lake and mineral spring waters, and brines. Seawater evaporation, and alkaline earths are removed by contains about 0.2 wt % MgO, whereas brines (either precipitation. Lithium carbonate is precipitated by the naturally occurring or obtained by solution mining of solid addition of a solution of sodium carbonate to hot brine.
salt beds) contain the equivalent of 4-20% MgCl . Among the magnesium minerals resulting from evaporation of New Zealand occurrence
ocean waters are carnallite (2KCl.MgCl .6H O), langbeinite Lithium is present in dilute brines found in the geothermal (K SO .2MgSO ), kieserite (MgSO .H O), epsomite fields of the Taupo Volcanic Zone (Fig. 2). Concentrations (MgSO .7H O), tachyhydrite (2MgCl .CaCl .12H O), and are typically 10-13 ppm Li, along with higher concentrations of silica, chloride, sodium and potassium. The Wairakeigeothermal field alone discharges about 445 t of lithium Properties
annually in geothermal waste water, into the Waikato River.
Magnesium is one of the alkaline-earth metals of Group In the 1980s, experimental trials were carried out to recover IIa of the periodic table. It is a light, silvery-white, and lithium and a variety of other elements including gold, silver, fairly tough metal that is malleable and ductile when heated.
silica, arsenic, cesium and rubidium, from geothermal Except for beryllium, magnesium is the lightest metal that waters (Roberts, 1986). Before lithium extraction, the remains stable under ordinary conditions. It tarnishes waters were pretreated to precipitate out most of the silica.
slightly in air, and finely divided magnesium readily ignites blue (crystalline);yellow (cryptocrystalline) white, grey,yellow, brownish,green, black Talc (steatite; soapstone) pale to dark 1 Table 3: Properties of some magnesium minerals.
upon heating in air and burns with a dazzling white flame.
magnesite occurs in veins varying in width from a few At room temperature, the metal is not attacked by oxygen, millimetres to several metres, and formed by the action of water or alkalies, but it is a very strong reducing agent, and carbon dioxide charged water percolating down or rising reacts with most acids to liberate hydrogen, and displaces up through serpentinised fissures and converting serpentine to magnesite. Examples include Kraubath, Austria;Chalkidhiki Peninsula and Euboea Island, Greece; Kilmar, The pure metal has low structural strength, so alloys have Quebec, Canada; Liaoning Province, China; Overton, been developed, principally with aluminium, zinc and Nevada, and Needles, California, USA; Kunwarara and manganese, to improve its hardness, tensile strength, Marlborough, Queensland; Thuddungra and Fifield, New resistance to saltwater corrosion, and ability to be cast, South Wales; Ravensthorpe, Western Australia; and The properties of some magnesium minerals are listed in Several magnesite deposits in Australia are at an advanced stage of exploration or development, for example LeighCreek in South Australia (resource of 474 Mt magnesite), Formation
and the Arthur River/Lyons River, Savage River and Main Magnesium deposits include deposits of magnesite, seawater Creek deposits in the Arthur Metamorphic Complex of and brines, and contact metamorphic deposits of brucite along granite-dolomite contacts (e.g. Malyy Khingan,Russia; Marble Canyon, Texas, USA). Magnesia is produced from surface or subterranean brines in the USA, About 10% of the magnesium produced is used in metallic form, mostly to prepare light metal alloys. Up to 5% is Natural magnesite occurs in a few, but very large, high grade added to most commercial aluminium. Magnesium is also (70-90% MgCO ) crystalline magnesite deposits and a large added to zinc that is to be used for die-casting or in wrought number of small, lower grade (>12% MgCO ) deposits of forms, to improve creep strength. The light metal alloys amorphous or cryptocrystalline magnesite. The crystalline are employed largely for structural purposes where a high deposits form by replacement of sedimentary dolomite by ratio of strength to weight is advantageous, including magnesite, either by hydrothermal alteration or aircraft and automotive parts and in portable tools, luggage metamorphism. Examples include Veitsch, Styria, Austria; trim, materials-handling equipment, artificial limbs, optical Slovakia; Navarra, Spain; Satka, Russia; Serra des Eguas, instruments and outdoor furniture. The unalloyed metal is Bahia, Brazil; Mount Brussilof, British Columbia, Canada; used in flashlight photography, flares, and pyrotechnics, Gabbs, Nevada, USA; and Jabal Al Rokhan, Saudi Arabia.
incendiary bombs, as a deoxidizer in the casting of metals, The amorphous magnesite deposits are formed by alteration and as a getter, a substance that achieves final evacuation of serpentine or allied magnesium-bearing rocks. The About 90% of magnesium production is used in nonmetallic producers have been the Takaka #4 lens, which produced applications, principally for the production of high 568 t at 60% MgCO in 1967, and the Takaka #2 lens.
temperature refractories. Magnesium carbonate is used asa refractory and insulating material, in pharmaceuticals, The talc-magnesite and quartz-magnesite lenses are derived glass ceramics, rubber and paints, and fertilizers; magnesium from serpentinite of the Cobb Igneous Complex chloride is used as dressing and filler for cotton and woollen outcropping southwards between the Cobb and headwaters fabrics, in paper manufacture, and in cements and ceramics; of the Takaka River. Wellman (1942), noted four major magnesium citrate is used in medicine and effervescent lenses of magnesite rock, and assessed their grades and beverages; magnesium hydroxide is used in medicine as the resources. In the #1 lens, magnesite content ranged from laxative “milk of magnesia,” in sugar refining, pulp and 44 to 79%, averaging 63%. The lens boundaries are not paper manufacture, and in water treatment; magnesium exposed, but Wellman roughly estimated that it had a length sulphate is well known as Epsom salt, and is used in of 500 m and maximum width of 8 m, based on the pharmaceuticals, chemicals, paper sizing and explosives; distribution of surficial float boulders. The larger #2 talc- magnesium oxide, called burnt magnesia, or magnesia, is magnesite lens had a length of 1550 m and maximum width used as a heat-refractory and insulating material, in of 220 m, and grades ranged from 35-66%, with most of cosmetics, as a filler in paper manufacture, and as a mild, the material at about 45%. Higher grade material, antacid laxative; and organic magnesium compounds averaging 70% MgCO , was found in the #3 lens, although (Grignard’s reagents) are used in the production of silicones length and maximum width (590 x 5 m) were less. The #4 and other organic compounds, and in the manufacture of lens is the western-most and largest of the four (1740 m length by 820 m maximum width). The lens showedrelatively consistent grades of 40-60% MgCO , with highest Magnesium metal prices ranged between US$2,450 and Wellman (1943) described eight talc deposits hosted in US$2,600 per tonne for product containing 99.8% Mg, inAugust 1999 (Mining Journal, August 20, 1999).
serpentinite of the Cobb Intrusives and located in the headof the Takaka River, in the Waikoromumu River, and in World production and consumption
World production of primary magnesium was 451,500 t in Ultramafic bodies containing lenses of serpentinite, talc- 1998, with production from countries including China magnesite, and steatite within the Waingaro Schist at (120,000 t), USA (117,000 t), Canada (57,000 t), Norway Richmond Hill, near Collingwood, were investigated by (49,000 t), Russia (35,000 t), Israel (25,000 t), France Lime & Marble (Riley, 1972; Thompson, 1989), and four (16,000 t), Kazakhstan (10,000 t) and Ukraine (10,000 t).
zones, containing lenses up to 200 m in length, were Magnesium resources are vast. The main sources, dolomite, seawater, brines, salt beds and magnesite, are widelydistributed throughout the world. The major deposits ofcrystalline magnesite are located in the USA, Canada, theCIS, North Korea, China, Greece, Czechoslovakia,Australia, Austria, Brazil, India and Nepal. The totalresources are estimated to be about 2800 Mt. The majoramorphous or cryptocrystalline deposits are located inGreece, Turkey, Australia and India. The main brinedeposits are located in the USA, Mexico, and in theevaporite-salts basin stretching from Scotland to the southof Poland.
Ore processing, smelting and refining
Magnesium is commercially produced by electrolysis of
molten magnesium chloride processed mainly from brines,
wells and seawater, or by the direct thermal reduction of its
compounds with suitable reducing agents, as in the Pidgeon
process where calcined dolomite is reduced with ferrosilicon
in a retort at 1150oC.
New Zealand occurrence
Magnesite occurs along with talc in ultramafic rocks in
Northwest Nelson, Westland, north Otago and Southland
(Officers of New Zealand Geological Survey, 1970b;
Williams, 1974; Fig. 3).
The Cobb-Upper Takaka district has been a small producerof talc-magnesite for agriculture and industry, butproduction ceased in the 1980s. Production between1944-61 totalled 9125 t, mainly for use as fertiliser in thetobacco-growing industry (Coleman, 1966). The largest Figure 3: Location of magnesite (and talc) deposits in New Zealand.
Talc-magnesite also occurs along shear zones in the Jachymov (Joachimsthal) in the Czech Republic. It was serpentinitic matrix of the Patuki and Croisilles melanges first isolated in the metallic state in 1841 by Eugène- of east Nelson. Although some is of very high grade, the Melchior Péligot by the reduction of uranium tetrachloride with potassium. The radioactive properties of uranium werefirst demonstrated in 1896 when the French physicist Talc-magnesite is present as segregations and veins within Antoine Becquerel used the fluorescent salt, potassium serpentinite of the Pounamu Ultramafics (Officers of New uranyl sulphate to produce an image on a photographic Zealand Geological Survey, 1970b). All known deposits plate covered with a light-absorbing substance. Otto Hahn are small and poor access is a major limiting factor to and Fritz Strassmann discovered nuclear fission in uranium potential future development. Most are impure mixturesof talc, calcite, and dolomite, although some are of good in 1938. In early 1939, Enrico Fermi suggested that quality, locally recrystallised, massive material. The colour neutrons might be among the fission products and could is usually grey, but in some cases it has a pale green shade continue the fission as a chain reaction. This was confirmed and thin pieces may be translucent. Occurrences include: by Leo Szilard, Herbert Anderson, Jean-Frédéric Joliot-Curie, and their coworkers. These discoveries led to the (a) Soapstone Creek on the northern side of the Taramakau first self-sustaining nuclear chain reaction in December 2 River where the main band is 6 m wide and of good 1942, the first atomic bomb test in July 16 1945, the first atomic bomb dropped in warfare in August 6 1945, and (b) an un-named northern tributary of the Taramakau River; the first nuclear-powered electrical generator in 1957.
(c) Taipo Gorge where a band of impure talc is up to 15 m Uranium was named by Klapworth after the then recently (1781) discovered planet Uranus, in turn named after theGreek god Uranus, the ruler of the sky or heavens (d) in the headwaters of Griffin Creek, where several lenses (Ouranos). Coffinite, one of the main uranium ore minerals, contain good quality, though generally impure, talc; was named in 1954 after R.C. Coffin, a Colorado (e) between the old serpentine quarry and the summit of Geological Survey staff member. Pitchblende (uraninite) is Mount Griffin where a talc lens of fair quality is present; from the German pechblende (pech = pitch, blende = to (f) Whakarira Gorge (Kokatahi River) where rather impure deceive). Thucholite was coined in 1928 from the chemical symbols for thorium, uranium, carbon, hydrogen, oxygen+ lite, which is from Greek lithos for stone.
(g) on Mt Jumbletop where there is a band of impure talc Major ores and minerals
Uranium metal is unknown in natural settings, as aresulphides, selenides and tellurides. The main ore minerals are the oxides uraninite (pitchblende), coffinite, brannerite Minor talc-magnesite occurrences are present in ultramafic and davidite (Table 4). More than 100 secondary rocks in northern Otago and Southland.
(supergene) uranyl (UO )2+ minerals are known, of which the most common are gummite, schroekingerite, zippeite, Production and resources
autunite, torbernite, carnotite, tyuyamunite and Both talc and magnesite have been produced from the Cobb deposits for use as a fertiliser, with a total recordedproduction of 108 t of talc and 21 802 t of magnesite. Last Properties
production of magnesite was in 1981 (308 t).
Uranium has the highest atomic number (90) of the naturally The largest deposit is at Richmond Hill near Collingwood, occurring elements. It is one of the actinide series of 14 where four lenses cover more than half a hectare. There is elements in Group IIIB (Th to Lr) of the periodic table.
no up-to-date estimate of the quantity or grade.
The actinides are similar in some respects to the lanthanide(rare earth) series of element (Ce to Lu), however, chemically, uranium resembles elements of Group VIB and thus hassome marked similarities to chromium, molybdenum and The use of magnesium is expected to increase in the automobile industry and in steel desulphurisation. Several automobilemanufacturers have invested in producing operations to secure Uranium is a silvery white metal that is malleable, ductile, a source of magnesium for their products. For example Ford a little softer than steel, and has a specific gravity of 19. It have purchased a magnesium operation in Queensland and is slightly paramagnetic and a poor conductor of electricity.
Volkswagen have a 35% share of a magnesium plant on the It is capable of taking a high polish, but in air, the metal Dead Sea. Auckland Anodisers Ltd have recently developed becomes coated with a layer of oxide, and when finely a new anodising process for magnesium to increase use of divided it ignites spontaneously (pyrophoric). Uranium is magnesium in such items as automobiles, power tools, ladders, strongly electropositive and, in a finely divided state, reacts with cold water. Acids dissolve the metal, but it is unaffectedby alkalis. Uranium has fourteen isotopes, all of which are radioactive. Naturally occurring uranium comprises threeradioactive isotopes: 99.275% 238U, 0.720% 235U and Discovery and origin of names
0.0054% 234U. Fission of 235U releases large amounts of Uranium was discovered in 1789 by the German chemist energy. Much of the internal heat of the earth is thought to Martin Klaproth, who identified the oxide in uraninite from be attributable to the presence of uranium and thorium.
Table 4: Properties of some uranium minerals.
Formation
and replacements forming lenses and pods, typically as Deposits of uranium are formed in a wide variety of flattened cigar-shaped ore bodies. A few deposits contain diagenetic, hydrothermal and weathering processes. The significant amounts of nickel, cobalt, arsenic and gold. The main deposit types are unconformity-related deposits, deposits are typically high grade (0.3-12.0% U) and contain sandstone uranium deposits, quartz pebble conglomerate 20,000-200,000 t U. Their genesis is controversial but deposits, hydrothermal vein deposits and sedimentary probably involved syngenetic concentration in the basement breccia deposits described below. In addition, other less host rocks, followed by enrichment during deformation and important deposit types include intrusive-related deposits metamorphism, followed by some late supergene (e.g. Rossing in Namibia), collapse breccia pipe deposits enrichment. Examples include Key Lake, Rabbit Lake, Cluff (e.g. the Arizona Strip in northern Arizona, USA), contact Lake, McArthur River and Eagle Point in the Athabasca uranium deposits (e.g. Mary Kathleen, Queensland, Basin, Saskatchewan, Canada; and Jabiluka I and II, and Australia), volcanogenic uranium deposits (e.g. Sierra Pena Ranger I and III in the Pine Creek Geosyncline, Northern Blanca, Chihuahua, Mexico), and surficial uranium deposits (Yeelirrie, Western Australia) (Eckstrand, 1984; Cox andSinger, 1986; Finch, 1989; Eckstrand et al., 1995).
Sandstone uranium deposits
Sandstone uranium deposits constitute about 32% of world
Unconformity-related vein uranium deposits
resources, but their production is declining with the Unconformity-related uranium deposits account for about increased importance of unconformity related deposits.
one third of world recoverable resources and current Sandstone uranium deposits are formed in fluvial or lacustrine, production of uranium. In these deposits, uranium is quartzose sandstones of Mesozoic or Tertiary age. The concentrated along faults and fracture zones at the uranium is transported in oxidised form in groundwater unconformity between a middle Proterozoic fluvial through the permeable clastic rocks and deposited on sandstone sequence and underlying pre-Middle Proterozoic encountering reducing conditions (carbonaceous matter, basement metamorphic rocks, such as graphite-mica schist, sulphides or methane) at a “redox front”. Uraninite, biotite-garnet schist and dolomitic marble, representing coffinite, pyrite and marcasite either fill the pore spaces marginal marine sedimentary sequences. Uraninite, and matrix or replace organic matter and rock grains coffinite, and hematite occur in stockwork veins, breccias unevenly to form tabular and crescent-shaped bodies, that may have a “c” shaped cross-section - the classic roll front.
La Crouzille area, Massif Central, Vendee district, and Individual deposits are mostly in the range of 1000 to 10,000 t of contained uranium in ores grading 0.03 to 0.2%U, but collectively they can form deposits that total more than 100,000 t of contained uranium. Examples include The main use of uranium is in nuclear reactors to produce Colorado Plateau, Lucky Mac mine, Wyoming; Jackpile about 20% of global electricity from the heat released by mine, New Mexico; Blizzard, Kelowna, B.C., Canada.
Quartz pebble conglomerate uranium deposits
Manufacture of enriched uranium for use in reactors Quartz pebble conglomerate or pyritic paleoplacer deposits produces byproduct depleted uranium, a very dense material represent about 20% of world uranium resources but that has pyrophoric properties on impact. Depleted production has declined dramatically in the last few years uranium is used chiefly for armour-piercing projectiles and with the closure of mines in Ontario, Canada. These for counterweights and ballast weights in internal guidance deposits contain uranium-bearing conglomerate and devices, gyro compasses, aircraft control surfaces, and sandstone that were deposited in braided streams and missile reentry vehicles, and as a shielding material.
alluvial fans during the Precambrian. The conglomerates Uranium metal is used for X-ray targets for production of are clast supported with well rounded pebbles of quartz, high-energy X-rays; the nitrate has been used as a chert, and locally pyrite, in a matrix of quartz, mica, chlorite, photographic toner, and the acetate is used in analytical pyrite and fuchsite. They contain pyrite, uraninite, chemistry. Crystals of uranium nitrate are triboluminescent.
brannerite, native gold, and traces of platinum group Uranium salts have also been used for producing yellow minerals. A major textural difference from sandstone uranium deposits is the occurrence of the uranium mineralsas detrital grains rather than in the matrix. Examples include Blind River-Elliot Lake, Ontario, Canada, the Uranium oxide (U O ) prices began rising in 1995, after a Witwatersrand in South Africa, Jacobina in Brazil and ten year trend of decreasing prices, and peaked in mid 1996 Tarkwa in Ghana. The Blind River-Elliot Lake deposits at US$16.50/lb. They have since fallen with prices in August contain 0.10-0.14% U, little gold and some by-product 1999 quoted between US$8.20/lb and US$10.00/lb (Mining thorium, whereas the Witwatersrand contains 0.03-0.06% Journal, August 20, 1999). Highest prices were achieved U and yields uranium mainly as a by-product of gold mining.
in the late 1970s when prices topped US$43/lb during theCold War arms build-up and the oil-price related energy crisis, Sedimentary breccia deposits
and the lowest price since that time was in 1991, US$7.25/ Olympic Dam hematitic granite breccia type is a major new lb, because of dumping by the countries of the CIS.
type of deposit which was discovered at Olympic Dam,South Australia, in 1975. This single deposit contains an World production and consumption
indicated resource of the order of 450 million tonnes at In 1996, world uranium production was 35,324 t U from 2.5% Cu, 0.08% U, 0.6 g/t Au and 6.0 g/t Ag, and represents 25 producing countries, whereas annual consumption for nearly 10% of world uranium resources. The mineralisation the more than 400 nuclear reactors currently operating is is hosted in hematitic granitic breccias of late Precambrian around 64,000 t U per year, requiring about 29,000 t U age that were formed by a variety of hydrothermal, draw-down on inventories (Kidd, 1997). This shortfall is magmatic, sedimentary and tectonic processes in a met by recycling spent fuel, the draw-down of existing continental rift setting. At Olympic Dam a very large uranium supplies, and blending down of military material.
orebody of disseminated chalcopyrite-bornite-chalcocite is The main producing countries (with 1996 production) accompanied by gold, uranium, silver, rare earths, barium include: Canada (11,788 t), Australia (4,974 t), Niger and fluorine minerals. Deposits in Zambia, Zaire, and the (3,320 t), USA (2,420 t), Russia (2,000 t), Namibia (2,452 Ailik Group in Labrador, Canada, may also belong to this t), South Africa (1,440 t), Kazakhstan (1,320 t), Uzbekistan (1,500 t), France (930 t), China (500 t), Gabon (565 t),Czech Republic (600 t), Ukraine (500 t), Spain (225 t), Hydrothermal uranium vein deposits
Hungary (200 t), India (200 t), Brazil (125 t), and Romania Hydrothermal uranium vein deposits, also known as Classical uranium vein deposits, represent about 10% ofworld uranium resources. They are veins, breccias and “World outside centrally planned economic areas” stockworks associated with steeply dipping fault zones in resources, defined as reasonably assured resources at a cost Proterozoic gneiss, schist and granite. The orebodies range of <US$80 per kg U, were estimated at 1.6 Mt U in 1986.
from a few centimetres to a few metres in thickness, rarely About 90% of these resources are in Australia, Brazil, up to 15 m, and extend down dip for a few hundred metres, Canada, Namibia, Niger, South Africa and the USA.
with some deposits in the 1 to 2 km range. The veins containcarbonate and quartz with uraninite, coffinite, and hematite Ore processing, smelting and refining
or iron sulphide. Some deposits contain a complex Preliminary treatment of ore may involve a roasting mineralogy grading into the five element (Ag-Ni-Co-As-Bi) operation, a physical or chemical concentration step, or a vein deposits described in the nickel mineral commodity combination of these. Chemical concentration involves report (Christie and Brathwaite, 1995b). Classical veins leaching by either dilute sulphuric acid or sodium carbonate contain 5000-15,000 t U at typical grades of 0.15% to and recovery of uranium as ammonium uranate or sodium 0.25% U, although grades may be as high as 1% U.
uranate (yellow cake) by precipitation with ammonia or Examples include Schwartzwalder, Colorado; Jachymov and with sodium hydroxide. The concentrate is treated Pribram districts, Czechoslovakia; Shinkolobwe, Zaire; and chemically to give a uranyl nitrate solution that can be further purified by solvent extraction to give uranium nitrate Hawks Crag Breccia and Watson Formation of the Pororari crystals. The nitrate serves as a starting material for other Group. The Hawks Crag Breccia is a coarse angular breccia compounds, such as oxides. In large-scale processing, the with thin carbonaceous siltstone and arkosic sandstone nitrate is decomposed thermally to give UO , which is beds, and is mainly derived from granite of the Paparoa subsequently reduced with hydrogen to form UO . UF is Range and from the Greenland group greywacke (Tulloch prepared by treating UO with HF gas. Uranium metal can and Palmer, 1990). It is commonly red coloured, due to be prepared from UF by electrolyses of UF in a salt bath hematite staining of feldspars. The Hawks Crag Breccia or by metallothermic reduction of finely divided UF with and Watson Formation were deposited in fault angle calcium or magnesium in steel bombs lined with fused depressions as alluvial fan and river flood plain deposits.
Tulloch (1988) has related the uranium mineralisation tothe circulation of fluids via the Ohika Detachment Fault New Zealand occurrence and resources
zone at the contact of the Pororari Group with underlying The main occurrences of uranium in New Zealand are deformed granite of the Paparoa metamorphic core sandstone-type uranium deposits in the lower Buller Gorge and the Pororari River areas, although detrital uraninite Buller Gorge: Bedded uranium deposits are found in the
has been recorded in gold dredge concentrates at Taramakau Tiroroa Facies of the Hawks Crag Breccia, a mainly granite- River and Gillespies Beach in Westland, and prospecting derived arkosic facies typically consisting of poorly sorted has identified some radioactive dikes and granites in west and matrix-rich, arkosic sandstone, breccia and Nelson and Fiordland (Officers of the New Zealand conglomerate, containing carbonaceous streaks which Geological Survey, 1970a; Williams, 1974; Brathwaite and appear to preferentially host the uranium mineralisation.
Pirajno, 1993; Fig. 4). Uranium minerals found in New Uranium mineralisation is found on both the north and Zealand include: autunite, becquerelite, coffinite, ferghanite, south sides of the Buller River, but mineralisation is different gummite, meta-autunite, rutherfordine, sabugalite, schoepite, sklodowskite, torbernite, tyuyamunite, uraninite,uranophane and uranothorite (Railton and Watters, 1990).
North of the Buller River, at least 10 lensoidal uraniferoushorizons up to 60 cm in thickness were identified, however Sandstone uranium deposits
most interest was shown in three horizons (T-J, S-C and Sandstone-type uranium deposits, formed by groundwater Waterfall). Riley (1969) reported grades ranging from 0.89 leaching of uraniferous granitic source rocks and deposition to 2.34 lbs U O per short ton (2000 lb) over mining widths of uranium in permeable carbonaceous sandstones, are of 1.2 m and over limited strike lengths. Coffinite is the found in the lower Buller Gorge and the Pororari River predominant uranium mineral, typically found with areas as weak disseminations of coffinite and uraninite in carbonate (calcite and ferroan dolomite), pyrite and fluorite non-marine conglomerate-sandstone beds of Cretaceous (Beck et al., 1958; Wodzicki, 1959). Coffinite is presentinterstitially to clastic sand grains and pebbles. Thucoliteand uraninite are also reported as primary minerals(Williams, 1974). Secondary uranium minerals includeautunite, ferghanite, gummite, meta-autunite, rutherfordine,schoepite, sklodowskite, uranophane, saleeite,metatorbernite, tyuyamunite and thucholite (Beck et al.,1958; Riley, 1969; Williams, 1974).
South of the Buller River, and stratigraphically higher inthe Hawks Crag Breccia, at least one mineralised lens up to1.2 m thick is present but continuity along bedding wasnowhere proved for more than 90 m (Williams, 1974). Themain primary mineral is uraninite and there is a much widerrange of associated sulphides such as pyrite and chalcopyrite(Cohen et al., 1969).
Average grades are up to 0.1% U O over a limited section, but are generally much less. The vanadium content is verylow at about 0.03%. Beryllium and molybdenum aregeochemically anomalous.
Bullock Creek, Pororari River: Some 16 uraniferous zones
have been found within the Hawks Crag Breccia and the
underlying Watson Formation (Hope et al., 1959; Klaric,
1967; Laird, 1988). In the Hawks Crag Breccia, uranium
mineralisation is highly lenticular and is associated with
red granite boulders and thin carbonaceous seams. In the
Watson Formation (Pororari Formation of Hope et al.,
1959), more continuous uraniferous horizons occur in gritty
sandstone and siltstone with carbonaceous radioactive
seams and interbeds. The primary minerals thucholite and
uraninite have been identified. Average grades are in the
Figure 4: Location of uranium deposits in New Zealand.
CRA found that the uraniferous outcrops were lenticular, Beach, the thorite was assayed as 76.6% thorium oxide small and scattered. Assay results at five localities ranged and the uranothorite as 62.6% thorium oxide and 11.5% from 0.46 to 0.82 lb U O per short ton (2000 lbs), uranium oxide (Hutton, 1950). Although no production equivalent to 0.04%. Sample widths ranged from 0.8 to 1.8 figures are known, Nicholson (1955) estimated that during m, with outcrop lengths possibly up to 100 m (Riley, 1969).
gold dredging operations, 0.1 ton of uranothorite was beingrecovered per week. Based on this estimate and assay Subsequent work by Lime & Marble Ltd (Buller Uranium figures of Hutton (1950), Caffyn (1971) estimated that 147 Limited; Riley, 1969) included additional field surveys and pounds of thorium oxide must have been mined each week.
the driving and sampling of 35 m adits at two of the CRAlocalities. Average grades from the two localities were 0.5 Past production, resources and future potential
and 0.59 lbs U O /short ton, calculated over a mining width of 1.2 m, approximately equivalent to 0.025 and 0.03 wt There has been no recorded commercial production of % radiometric. The highest grade obtained was 6.4 lbs uranium from New Zealand deposits and there will be no production in the near future due to New Zealand’s nuclearfree legislation and the Minerals Programme for Minerals Fox River mouth: Carbonaceous streaks that are weakly
other than coal and petroleum which specifically does not radioactive (0.2-0.3 R/hr) are found at the southern end of allow prospecting, exploration and mining of the primary a 300 m long outcrop of leached Hawks Crag Breccia south of the mouth of the Fox River (Beck et al., 1958). Whittle(in Williams, 1974, p. 207) reported sporadic uraninite Future trends
grains up to 3 mm in diameter, in association with“abundant” chalcopyrite.
There is a trend of falling output in countries within theCIS, balanced by a rising output in the major western Big River: Hope et al. (1959) noted that weak radioactivity
producing nations. The future use of uranium lies in the had been detected in bedded material consisting of granite continued acceptance of nuclear-powered electricity generation, particularly in countries not enjoying alternative Waitahu River: The Hawks Crag Breccia consists of
energy sources for producing electricity. Shutdowns of alternating beds similar to the Blackwater facies and Tiroroa higher-cost reactors and the large-scale introduction of “B” facies in the Buller Gorge. Bedding is indistinct, except breeder reactors around the year 2010 suggest that there is in places where sandstone bands occur. Low levels of unlikely to be a major increase in demand for uranium.
radioactivity have been detected in some beds of the Tiroroafacies.
Zirconium
The Waitahu Breccia occurrence consists mainly of granite Discovery and origin of names
fragments of varying size, though a certain amount of The name zircon probably originated from the Persian word hornfelsic sandstone may be seen in some outcrops.
zargun, which describes the gold like colour of the gemstonenow known as zircon, jargon, hyacinth, jacinth, or ligure.
Other occurrences
This mineral, or its variations, is mentioned in biblical Occurrences have also been reported from a trachyte dike writings. The mineral was not known to contain a new within Hawks Crag Breccia in Batty Creek (Beck et al., element until 1789, when the German chemist Martin 1958), in a quartz veinlet in granitoids at Sinclairs Castle Klaproth analysed a jargon from Ceylon and found a new (Beck et al., 1958), and in hornfels and granite boulders earth, which Werner named zircon (silex circonius), and within the Hawks Crag Breccia from Big River and the Klaproth called Zirkonerde (zirconia). The metal was Buller Gorge (Wodzicki, 1959). At Batty Creek, uranium is isolated in impure form in 1824 by the Swedish chemist concentrated in veins and aggregates of zircon traceable Baron Jöns Berzelius. A higher purity metal was first over a distance of more than 40 m, with a maximum grade produced in quantity in 1925 by the Dutch chemists Anton of 0.28% U O . The Big River biotite hornfels boulder Van Arkel and J.H. de Boer by thermal decomposition of described by Wodzicki contained 0.18% U O , but the zirconium tetraiodide. In the 1940s, William Kroll of uranium-bearing phase could not be identified. Biotite Luxembourg developed his cheaper process of making the granite from the same area contained 0.025% U O . Biotite metal based on the reduction of zirconium tetrachloride by hornfels boulders from Batty Creek in the Buller Gorge were strongly radioactive (0.2%), and contained uraninite, thefirst occurrence identified in New Zealand (Wodzicki, Major ores and minerals
Zirconium is never found free in nature, but occurs most Fergusonite and samarskite have been found as rare alluvial commonly as zircon (ZrSiO ) and less commonly as grains in the Canaan Valley in west Nelson.
baddeleyite (ZrO ). Hafnium, a metal with properties similar to those of zirconium, is always present in zirconium West Coast beach sand
minerals, with an average Hf:Zr atomic ratio of Above average background radioactivity was first detected approximately 0.02, although a few minerals are rich in in blacksand during a wartime search for uranium hafnium (e.g. alvite: Hf, 13.6%; Hf:Zr, 0.54; thortveitite: (Nicholson, 1955) and was later shown to be due to trace Hf, 2.7%; Hf:Zr, 1.8). Other common impurities in zircon concentrations of thorite, uranothorite and monazite in and baddeleyite include thorium, uranium, rare earths, these sands (Hutton, 1950). Measurements of 238U in calcium, magnesium and iron. The U+Th content is Barrytown sand by Roberts and Whitehead (1991) indicated detrimental for environmental reasons and degrades the concentrations of about 30 ppm (0.003%), about one fifth minerals because the radioactive emanations from these the concentration of associated thorium. At Gillespies elements disorder the lattice structure.
Properties
fillers). With niobium, zirconium is superconductive at low Zirconium, is one of the transition elements in Group IVb temperatures and is used to make superconductive magnets.
of the periodic table. In its pure state zirconium exists in two forms: the crystalline form, a soft, greyish-white,lustrous, ductile metal; and the amorphous form, a bluish-black powder. When finely divided, the metal may Prices for zircon sand (66-67% ZrO ) were A$500-600/t ignite spontaneously in air, especially at elevated fob in August 1999 (Mining Journal, August 20, 1999).
temperatures. The solid metal is much more difficult toignite. Zirconium is exceptionally resistant to corrosion Ore processing
by many common acids and alkalis, by sea water, and by Zircon and other heavy minerals are concentrated from the other agents. It is used extensively by the chemical industry beach sands by gravity concentrators and magnetic and where corrosive agents are employed.
high-tension separators. Zirconium is produced by the Kroll Zircon is a transparent, translucent, or opaque mineral, process in which zirconium tetrachloride is reacted with with an adamantine lustre, hardness of 7.5 and a specific magnesium or sodium. When finely powdered zirconium gravity of 4.2 to 4.86. Zircon may occur as colourless is required, the calcium reduction of ZrO may be used.
crystals or in shades of green, grey, red, blue, yellow or Hafnium is separated from zirconium by solvent extraction brown. The high refractive index and dispersion of zircon cause it to approach diamond in fire and brilliancy. Severalvarietal names have been applied to coloured gems. The World production and consumption
clear, transparent yellow, orange, red and brown varieties Zircon is produced mainly as a byproduct of ilmenite and are known as hyacinth or jacinth; translucent or opaque rutile mining of beach sands in Australia (400,000 t in varieties, and most of the colourless types, are known as 1997), South Africa (Richards Bay Minerals 300,000 t in jargon or jargoon. When subjected to high temperatures, 1997), USA (Florida and Georgia), Brazil and India. Lesser zircons either change colour or lose their colour, and assume production is from baddeleyite ores at Phalaborwa, South a greater brilliance. Colourless zircons are known as Matura Africa in two different operations: one recovers the mineral diamonds or white zircons. A blue variety, produced by as a by-product of open-cast copper mining and another heat treatment and known as blue zircon, is also commonly recovers the mineral from phosphate feeds. It is also mined in Rockingham, Perth, Western Australia and Russia’s Kola Baddeleyite is a colourless, yellow, green, reddish or brownish black coloured mineral with a greasy to vitreouslustre, subconchoidal to uneven fracture, and is brittle. It Deposits of gem zircons are found in Sri Lanka, Madagascar, has a hardness of 6.5 and a specific gravity of 5.8.
Norway, and New South Wales, Australia.
Formation
New Zealand occurrence and resources
Zircon occurs as an accessory mineral in all types of igneous Zircon is widely distributed as an accessory detrital mineral rocks and is abundant in silica-rich rocks. It is extremely in titanomagnetite and ilmenite beach sand deposits of the resistant to weathering and concentrates along with some North and South islands (see the titanium mineral other heavy minerals in beach and alluvial sand deposits commodity report, Christie and Brathwaite, 1998b; Fig.
that may contain 0.2-3% of zircon. Zircon is mined as a 5). Detrital zircon also occurs in alluvial placers in Westland, coproduct of beach sand mining for titanium ores (see titanium mineral commodity report, Christie and Ilmenite beach sand deposits near Whitianga and at Brathwaite, 1998b). The main deposits are the relatively Wharekawa on the east coast of the Coromandel Peninsula young beach sands found on or near active coast lines of are reported to average 1% zircon (McLaughlin, 1973). If Australia, South Africa, USA, India, Sri Lanka, Malaysia, these deposits are ever mined for ilmenite, the zircon would be a potentially recoverable by-product.
The titanomagnetite beach sands on the west coast of the Most zirconium metal is used in the nuclear power North Island contain trace zircon but few details are known.
generation industry in cladding, fuel rods, for alloying with The Waikato North Head deposit, currently mined for iron uranium, and for reactor-core structures, because of its low ore by BHP New Zealand Steel, contains about 0.1% zircon neutron-absorption cross section, excellent corrosion which is potentially recoverable (Shannon et al., 1965).
resistance, heat resistance, strength, ductility and ease of The ilmenite beach sands of the West Coast, South Island fabrication. In many of these applications it is used as typically contain 0.1-0.39% zircon, with locally higher zircaloys, alloys which contain about 2% tin. Zirconium concentrations up to 0.5% zircon (McPherson, 1978; is also used as an alloying agent in the production of some Nicholson et al., 1966; Nicholson, 1967; Minehan, 1989).
magnesium alloys and as an additive in the manufacture of Beach sand at Orepuki, Southland, contains 0.1-1.1% certain steels. Other uses include the manufacture of porcelain and ceramics, refractories, explosive primers, flashbulbs, pyrotechnics, as a “getter” in vacuum tubes to remove In Westland, both normal colourless and purple hyacinth traces of gases, and in heat exchangers, pump housings, varieties of zircon were present in the heavy mineral fraction valves, and other equipment subject to corrosion by acids.
of concentrates examined by Hutton (1950) from Westland The chemical applications include adhesives, anti- gold dredges working Recent age river gravels at Arahura, perspirants, catalysts, and polymers (cross linking/special References
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Brathwaite, R.L.; Pirajno, F. 1993: Metallogenic map ofNew Zealand. Institute of Geological and Nuclear Sciencesmonograph 3. Caffyn, P.H. 1971: Report on the economic potential ofthe Gillespies Beach mineral sand deposit (Technical Report253): Carpentaria Exploration Company ProprietaryLimited. Unpublished open-file mining company report,Ministry of Commerce M1643.
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Christie, A.B.; Brathwaite, R.L. 1995b: Mineral commodityreport 10 - nickel. New Zealand mining : 39-45.
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Figure 5: Location of zirconium deposits in New Zealand.
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