Antimony (trioxide!) on the watch list

Published: Tuesday, 28 August 2012

Gerry Clarke discusses whether antimony is as scarce as indicated by the British Geological Survey last year and asks: Is there an opportunity to help head off a looming supply crisis?

By Gerry Clarke

In September 2011, a British Geological Survey (BGS) Risk List of 52 economically valuable elements put antimony at the top, ahead of the rare earths, based on scarcity, production concentration, reserve base distribution and governance. This trumped an earlier June 2010 European Commission report that bestowed critical status on antimony found to be sixth in terms of supply risk, below that of rare earths, and lowest, along with rare earths, in terms of importance to the European economy in the group of 14 identified critical elements and minerals.


In nature, antimony primarily occurs as the sulphide, stibnite (Sb2S3), its principal ore mineral amongst a hundred or more mineral species often associated with lead, copper, silver and gold mineralisation. With a crustal abundance value of just 200 ppb, antimony is rarer than each of the so-called rare earth elements and many of the other minor metals. Yet, ironically, it is amongst the oldest of recognised elements known to man once thought capable of turning lead into gold by 17th century alchemists.

Not only is antimony supply critical. It is also rare.

Antimony trioxide is prime concern

Counted in the ranks of the MMTA’s 49 minor metals, alongside the rare earths, antimony exhibits both metallic and non-metallic properties. Antimony trioxide (ATO), traditionally manufactured by roasting stibnite ore in furnaces at temperatures of 850-1,000ºC to produce crude trioxide and then sublimed to remove ever present arsenic trioxide, is the predominant supply side stibnite product from integrated resource-based companies. ATO may also be produced from stibnite via a chloride route and produced directly from base forms of antimony metal.

ATO, and a host of chemical derivatives  used in such traditional industrial minerals applications as chemicals, ceramics, glass, pigments, and filling compounds  takes the lion’s 75% share of the antimony market. So, the recognised acute supply problem is greater in terms of ATO and the non-metallic markets that rely on it.

If the chemicals industry could develop a total and effective ATO substitute for its flame retardant systems application, antimony would probably fall off its top risk (BGS) perch. But that doesn’t seem likely, although partial substitution by zinc stannates or borates in some formulations with little or no plasticiser has been successful.

Not only is there no effective total alternative in sight there is a regulatory obligation to use ATO-based flame retardants in certain manufactured goods such as plastics used in household appliances, televisions, computers, electronic devices, industrial electrical installations, furnishings for textiles and foam, building materials, electric cables, textiles, and transport. Flame retardants account for about 50-60% antimony’s non-metal use.

ATO does not have flame retarding properties on its own. But it is an effective catalyst and synergist for halogenated (Cl and Br) flame retardants. ATO facilitates the breakdown of halogenated flame retardants to active free radicals. ATO also reacts with the halogens to produce volatile antimony halogen compounds. It is these compounds that are directly effective in removing high energy hydrogen and hydroxide radicals that feed the gas phase of any fire. ATO therefore strengthens the flame suppressing effect of flame retardant chemicals. Added to PVC the ATO acts to suppress flames by activating the chlorine in the PVC polymer although ATO substitution in some rigid and semi-rigid PVC products is possible as there is in certain textiles. By their very nature ATO in flame retardants is not recyclable.

PET (polyethylene terephthalate), accounting for 10-15% non-metal usage, is mainly for synthetic textiles (60%), better known as polyester, and plastic containers (30%) and demand is growing with China leading both world production and demand at about 25% each. Although ATO in PET products isn’t recoverable, recycling of PET containers is increasing and some ATO substitution is possible. Other established uses include glass making where antimony is used to remove bubbles and to decolourise different types of glass, and in ceramics it is an opacifier for porcelain glazes.

The EU also identified antimony’s role in emergent technologies. In semi-conductors, alloys with germanium and tellurium are used in read-writable CD/DVDs. The same alloy has been used to make artificial neurons that act like a human synaptic nerve cell which promises much lower power consumption in supercomputers. Antimony tin oxide is an important component in electronics, optics, micro-capacitors, and, in a multitude of display panels such as iPads, its antistatic, infrared absorbance, and transparent conductivity enhances readability. More blue sky research has developed a liquid metal grid storage battery using antimony and magnesium.

On the metallic demand side

Bluish grey electro-refined antimony available in ingots, blocks, and powder increases hardness, strength and chemical resistance when alloyed with lead for use in batteries and when combined with tin, lead or copper, for anti-friction alloys. Alloyed with lead and tin it is a general purpose solder and with tin on its own is a standard plumbing alloy where antimony adds strength without affecting wettability and prevents tin pest. Finely divided antimony black is used to coat brass and lead alloys, and high purity antimony metal (99.999-99.99999%) is used in semi-conductors. Antimony is still used in small arms and sporting ammunition.

The bulk of secondary antimony is recovered as antimonial lead most of which is generated by the battery industry where it is re-consumed. Changing trends in that industry in recent years, however, have generally reduced the amount of secondary antimony produced and the trend to low-maintenance batteries has tilted the balance of consumption away from antimony and toward calcium as an additive.

Supply side diversification

Antimony and the rare earths share another common feature in that the world placed long term high level reliance on cheap supplies from China that are now fast diminishing.

In the case of antimony, complacency may be owed to generally declining antimony consumption in almost all sectors, excepting flame retardants, in the last quarter of the 20th century when there were mine closures exacerbated by cheap supplies from China. But supply restrictions were evident from mid-2005.

Not only are resources in China depleting, continuing operations are impacted by production quotas, export controls and environmental measures as has occurred with rare earths in far higher public profile. Furthermore, China is actively encouraging imports of antimony through interest subsidies and Chinese enterprises have been securing foreign supply positions.

Outside China the small balance of supply, around 11%, has come from Bolivia, South Africa, Russia, Tajikistan, and a number of others. In these countries and elsewhere the mineral resources industry has begun to respond to the deepening antimony shortfall risk though not yet to the same extent as in higher profile rare earths or lithium sectors which are seen basking in the growth of high tech industrial and consumer applications.

Antimony’s insatiable industrial applications; unseen, unglamorous but essential, are far removed from the headline-making clean energy, automotive and communications sectors and have not attracted anywhere near comparable attention.

But that is changing and opportunities for resource development appear undeniable. Antimony deposits are generally amenable to relatively low capital expenditure for well understood extraction methods, processing techniques, and refining methods. Individual deposits tend not to be large but may occur in structurally controlled proximity. There is no dominant corporate presence outside the Chinese enterprises and new developments are highlighting opportunities in countries with acceptable geopolitical risk. Compare all that with the complexities associated with brines-hosted lithium resources and the rare earths industry.

Whilst antimony production remains dominated by China, the rest of the world’s documented antimony producing regions are littered with small scale historical workings many of which are being revisited, explored and, in some instances, progressing towards rejuvenated operations. Project developments are split between East (Australia, China, Laos, Myanmar) and West (Canada, USA, Mexico, Bolivia) with projects in Italy, Turkey and UAE in or near antimony-sparse European markets and South Africa now moving forward.

China - consumption rockets whilst resources wane

Historically, antimony production has been split between state-run enterprises and the private sector, led by operations in Guangxi Province until the Nandan closures in 2001 gave pre-eminence to Hunan Province followed by Yunan and Guizhou. The best known antimony deposit in China is at Xikuangshan, Hunan near Lengshuijiang city which was first exploited in the 16th century.

Today, 550,000 tpa of ore is extracted from a mining area that extends through some 22.5 km2 at Xikuangshan. The operation is owned and run by Hsikwangshan Twinkling Star Co Ltd, a part of Hong Kong-listed Hunan Nonferrous Metals Co Ltd (HNC) that is now 100% owned by China Minmetals Corp after it acquired the 49% it didn’t already own in December 2011. HNC is the world’s largest antimony producer with total production capacity of 40,000 tpa of mixed antimony products. China’s domestic antimony consumption has risen 62% from 40,000 tonnes in 2006 to approximately 65,000 tonnes in 2011 although there was a slight dip in 2010 and 2012 consumption is expected to show further increase. In 2011 China imported about 59,960 tonnes of antimony concentrates, 33% above the 2010 level, and 245% higher than 2007 imports at 17,354 tonnes.

Hunan Province, once described as possessing the largest antimony resources in China and hosting 9.3% of the world’s antimony deposits, appears to now be running short of available antimony resources. For 12 months following March 2010 the local government in Lengshuijiang, which accounts for about 60% of world antimony supply, shut down 110 smelters in an environmental purge and only nine were allowed back on stream after furnace upgrades. All illegal producers were also shut. But officials in Lengshuijiang had also announced that after more than 110 years of continuous mining, the area now had only 5 years of mining life left. And USGS reports that, at present consumption rates, current reserves throughout China will be depleted by 2024.

Bolivia - dwindled significance perhaps resurgent

From around 20% of world antimony production in the 1980s Bolivia’s contribution is now about 3% but it remains a significant source of antimony ores and concentrates for North American markets.

About 5,000 tonnes were produced in 2011 (USGS). The three mines at Caracota, Chilcobija and Espiritu Santo are the traditional sources in the country’s gold-antimony belt of the Eastern Cordillera where there are literally hundreds of small deposits many exploited on a small scale for decades.

Planet Resource Recovery Inc, a US petrochemicals firm, entered into joint venture with Franklin Mining to develop and operate the San Antonio de Turiri antimony mine which comprises three separate vein structures. The mine is wholly-owned by Planet’s subsidiary, Raptor Ventures LLC. In September 2010 Raptor Ventures began operations at the Sorpresa mine in Bolivia’s antimony belt producing up to 300 tonnes per month contained antimony from high grade ore containing 58-67% Sb.

In 2010 the Bolivian government nationalised Glencore’s Vinto antimony smelting facility citing under investment as the cause. Besides ores and concentrates, antimony metal is produced and ATO production is also reported.

Peru - La Oroya back in business

Although not known as a producer of ATO, the country has a number of small mines producing ore and concentrates. One such is Peru Pacific Enterprise SAC that reports operating six small mines producing up to 400 tonnes a month. Peru is well known as a producer of antimony metal with 530 tonnes produced in 2009. Although in that year Doe Run Peru Co, part of US’s Renco Group, closed its La Oroya polymetallic smelting plant owing to financial and ensuing environmental problems. However, in July 2012 the company announced that it is to recommence operations starting with the zinc circuit. One imagines that antimony may come soon after.

South Africa - Cons Murch a new Village

That the Murchison range Archaean greenstone belt of north east Transvaal is host to antimony along with copper and gold has been known since 1869. Several commercially interesting antimony deposits stretch for over 50km in 50-100 metre widths in the central part of the Murchison belt that became known as the “Antimony Line”.

The deposits at Gravelotte, near Phalaborwa were first exploited on an industrial scale in 1934. However, in 1991 Consolidated Murchison emerged initiating a succession of corporate ownership that came to rest in June 2012 when Village Main Reef Ltd won final approval of its 74% majority acquisition of what had become known as Cons Murch. The balance of ownership is with an employee trust.

Today, the three operating shafts: Athens, Monarch and Beta are being deepened with increased mechanisation, making Gravelotte one of the largest antimony producing mines outside China. As at November 2011 antimony resources were 9.5m tonnes grading 2.17% Sb (with 2.44 grammes per tonne Au) with reserves of 993,000 tonnes grading 2.67% Sb. Head grade is 1.5% Sb whilst mill recovery is 80%. By-product gold is also produced. Mine production is increasing to 27,000 tpm of milled product and 11 years mine life is expected. Near surface ore is also being developed in the Alpha-Gravelotte complex where a surface decline is being driven to extract up to 7,000 tpa of antimony concentrates expected Q2 2013. Stibnite concentrates are exported to India (69%), Thailand (17%), and China (13%).

Canada welcomes Hunan

In February 2008, Beaver Brook Antimony Mine Inc, near Gander in Newfoundland, reopened after closure in 1998 owing to falling prices after only several months’ operation by Roycefield Resources Ltd.

North America’s sole producing antimony producer passed into Chinese ownership in October 2009 when Hunan Nonferrous Metals Corp and its wholly-owned subsidiary, Gander Antimony Mine Ltd, paid $29.5m in cash to be augmented by future annual production-based payments.

The stibnite ore is mined underground and fed to the 550 tpd mill, where flotation produces a 63% Sb concentrate which is trucked to Halifax for shipment to China. Mine life of 10 years is expected for what was described as the largest antimony mine outside China and South Africa capable of satisfying 5% of world demand when it reopened.

Tri-Star Resources plc is also exploring antimony anomalies over 170,500 hectares discovered by New Brunswick’s Department of Natural resources northwest of Fredricton.

USAC corralling its own resources in Mexico

When Sunshine Mining and Refining Co ceased silver mining operations at the Sunshine Mine in Kellogg, Idaho in 2001 the US ceased antimony mine production. Today, Silver Opportunities Partners LLC (SOP) is working to reopen the mine that it bought from Sterling Mining Company in 2010 for $24m. Sterling, which filed under Chapter 11 protection in 2009, acquired the rights mid 2003 and briefly operated the mine from December 2007 until last closure in 2008. As yet it is not known when Sunshine will recommence but if, and when, it does by-product antimony could also reappear.

Until that might occur, United States Antimony Corp (USAC) remains the only significant producer of antimony products in the US based on third party raw material sources although that is changing owing to developments in Mexico. USAC ceased underground mining operations in December 1983 owing to the availability of cheaper foreign sources. However, USAC has continued production of antimony oxide, sodium antimonate, antimony metal, and precious metals at its antimony smelter and precious metals plant west of Thompson Falls, Montana. In response to the US Department of Defence’s interest in the use of antimony trisulphide in ammunition primers USAC is presently constructing an additional facility for its production.

In 2011 USAC’s sales volumes for antimony oxide and metal were 762 tonnes and 636 tonnes respectively, similar to 2010, although significantly higher prices yielded a 66% improvement across all products in value terms. However, USAC estimates that its share of the domestic market for antimony oxide products is only 4%.

In April 1998, USAC formed United States Antimony SA de CV (USAMSA) to mine and smelt antimony in Mexico. Three divisions are operated: the Los Juarez mineral deposit, including concessions in Queretaro, that will start producing in 2012; the Puerto Blanco flotation mill at San Luis de la Paz, Guanajuato also starting in 2012; and the Estacion Madero smelter in the Municipio of Parras de la Fuente, Coahuila which began operating in 2011.

USAC is now accelerating the development of Los Juarez whilst substantially increasing mill and smelter capacity during H2 2012. As of July over 5,000 tonnes of Los Juarez mill feed derived from the Minas Grande Zone is ready for processing at the Puerto Blanco flotation plant. Los Juarez East is also being developed for underground mining whilst a third zone is earmarked for later development.

A 500 tpd ball mill and flotation plant shipped from Montanna to Puerto Blanco, along with other equipment already installed, will raise the company’s total milling capacity from 150 tpd to 650 tpd. The Madero smelter has the capacity to produce up to 100 tpm of crude antimony trioxide which is shipped to the Montana plant to produce finished products. All four furnaces at the Madero smelter have been retrofitted to process additional feedstock from seven Mexican antimony mines, including two under option to USAC, and there are plans to add a further four furnaces to the facility subject to permitting. At the same time conversion to natural gas from propane is expected to save the company 70% in energy costs.

Australia - Hillgrove watching newcomers enter

Straits Resources Ltd is still looking to divest its Hillgrove antimony and gold mine near Armidale, NSW. A deal with Emu Nickel NL fell though in May 2012 because fundraising failed to reach the agreed A$60m required. Having ceased production in August 2009 it had been thought that mining at Hillgrove would be back in production in 2013 with up to 5,000 tonnes of antimony and 25,000 ounces of gold pa.

Mandalay Resources acquired the Costerfield, Victoria gold-antimony mine from Western Coal in December 2009 (acquired from Cambrian Mining plc in July 2009) and immediately began mining. The Costerfield veins were discovered in the 1860s and have been mined intermittently on a small scale for both gold and antimony. More extensive exploration resulted in the construction of a processing plant in 1995 to re-treat tailings and the oxide portion of the Brunswick open pit and a successful feasibility study on the Augusta deposit, discovered in the 1970s, led to underground mining in 2006.

Mandalay attained the planned production rate in excess of 5,000 tpm by end 2010 and through the end of 2011 generated new reserves deeper on Augusta’s east and west lodes being mined. Production for Q2 2012 was up 48% year-on-year at 612 tonnes contained antimony and 2012 looks set to substantially exceed 2011 production of 1,575 tonnes. The product is shipped to China.

In 2011, the Cuffley lode was discovered just 500 metres north from Augusta and, by the end of the year, an initial high-grade inferred resource was established that forms the basis for a Preliminary Economic Assessment for completion end 2012. Cuffley’s gold and antimony grades are significantly higher than Augusta. Proven and probable reserves are 88,410 tonnes at 5.9% Sb and measured and indicated resources are 482,300 at 4.9% Sb with associated gold.

The Wild Cattle Creek antimony gold deposit in northwest NSW, worked intermittently since the 1800s and last mined in the 1970s, is part of Anchor Resources’ Bielsdown exploration project which is one of three in the state that has resources estimates at three different cut-off grades. Anchor’s two other antimony projects are to the south at Munga and to the west at Thunderbolts. At the mid 0.5% Sb cut-off grade indicated and inferred antimony resources at Wild Cattle Creek were 1.06m tonnes grading 1.77% Sb. In May 2010 China Shandong Jinshunda Group Co Ltd, an integrated minerals and materials engineering group founded in 1986, acquired Anchor Resources.

In Western Australia, Northwest Resources Ltd is developing its Blue Shear gold-antimony project north of Nullagene, eastern Pilbara. Resources amounting to 646,000 tonnes containing 1.2%Sb have been identified. A definitive feasibility report is expected by end 2012 and, if positive, Northwest plans to develop an underground mine producing up to 1,500 tpa antimony over a 5-year mine life starting 2013.

Turkey hosts Europe’s leading ATO producer

The country’s antimony mining industry has been largely dominated by Ozdemir Antimony Mining Joint Stock Co based on mines in the Turhal district of Tokat Province in northern Turkey. Dutch corporation, Advanced Metallurgical Group NV (AMG) is now active in the country as is newcomer Tri-Star Resources.

AMG, Europe’s largest ATO manufacturer processing over 10,000 tons antimony metal equivalent products each year, acquired antimony mining rights and an adjacent smelter in Turkey in 2010. AMG’s Sudamin Holdings is a major European enterprise in ATO-based flame retardants and through its wholly-owned subsidiary, Suda Maden AS, operates the antimony mine and processing plant. Sudamin has two independent ATO manufacturing plants in France at Chauny, Societe Industrielle de l’Aisne, and at Laval, Produits Chimiques de Lucette .

Formed in August 2008, Tri-Star Resources plc acquired a mining permit and exploration rights on the site of historic small scale workings near Goynuk village in the Murat Dagi Mountains of Kutahya Province. Second phase drilling of high grade pods of antimony ore, hosted in silica-rich rocks, was completed in January 2012 and initial tests indicated the potential to produce high grade 61.1% Sb concentrates. Meanwhile, Tri-Star has secured an environmental permit to treat to 14,000 tpa of existing stockpiled material at Goynuk. Roasting tests are being performed by Hazen Research, Inc in Denver, US.

The company’s joint venture with Union Group International, Tri-Star Union Minerals LLC, is to establish a 20,000 tpa plant over 20 hectares in the Ras Al Khamaih free trade zone in United Arab Emirates. The $123m project is for 25 years design life for high-tint low-lead milled ATO powders and antimony metal ingots production.

The grand scale project has also been evaluated for 50% production, 10,000 tpa, reflecting the risk that Tri-Star may not be able to source sufficient raw material. It has been estimated that Tri-Star’s present Turkish properties will only account for about 4,000 tpa production. In addition to using its Turkish feedstock not only is Tri-Star looking to secure additional feedstock sources (see Canada and Myanmar) it also plans to offer toll processing to third party concentrates suppliers.

Italy - Adroit resurrecting Manciano

Vancouver-based Adroit Resources Inc is exploring to reinstate antimony mining in the former producing region of Manciano, Grosseto Province, Italy. Adroit’s work so far on just two of six permits, that have historic, non-compliant, resources of over 45,000 tonnes contained antimony, suggest these two permit’s resources can be raised to over the company’s minimum compliant resources target of 100,000 tonnes.

In June 2012 Adroit added three new antimony exploration permits to the seven it already had taking total exploration area to 3,835 hectares. One of the three new permits at Valle Lupara contains the former Montauto mine, which produced 97,724 tonnes of ore grading 1.7-2% Sb. The other two, Catabbio and Selvena, host historical mercury mines that recorded significant antimony mineralisation.

The company is aiming for a Canadian NI43-101 compliant resources estimate next year and to go on to develop a 10,000 tpa antimony mine, probably with gold and silver credits, for ten years mine life which, according to Adroit, would make Italy the largest producer outside China.

Mainland Southeast Asia holding promise

Myanmar is one country in the region producing raw ore for export to China that is now getting increased exploration attention. Laos also exports raw ore to China.

Tri-Star Resources has entered into a collaborative agreement with RDP Singapore Ltd (RDPS), a subsidiary of London-based finance house Resource Development Partners Ltd, in relation to the latter’s antimony exploration project surrounding two existing antimony producers in Myanmar. If successful Tri-Star will likely seek some form of marketing or offtake agreement for supplies to its joint venture UAE plant. In 2011 Myanmar produced over 14,000 tonnes of antimony in raw ore form destined for China. New developments are also in eastern Kayah and south eastern Karen states.

In Laos, Sin Rung Roj Supply Co Ltd (SRS) is an export orientated small to medium scale mining company exploiting copper, lead and antimony deposits throughout the country. Raw ore is taken to the company’s crushing plant in Vientiane which has 60,000 tpa capacity mainly for copper but up to 20,000 tpa of antimony ore (40% Sb) is able to be processed for export to China.

Elsewhere in Indo China, antimony deposits spread through Thailand were worked intermittently during the 1970s. Peak concentrates production averaging 42.5% Sb was in 1972 at 11,000 tons. Vietnam and Cambodia may also prove interesting for antimony.

Japan long reliant on imports

Japan has a history of antimony mining and derivate chemicals production that declined owing to availability of cheap imports. Nihon Seiko Co Ltd is a leading dedicated producer of antimony metal and ATO in Japan that originated in 1948 based on ores from its Nakase mine. But as early as 1952 the company switched to using imported material. Several others also produce ATO in Japan. A recent find in the sea bed of the shallow seas by Amami-Oshama Island, Kagoshima Prefecture, is a high grade antimony deposit that might prove interesting if supplies remain very tight.

Filling the gap

It’s a statement of the obvious that the key to solving antimony’s, in particular antimony trioxide’s, critical availability problem lies in developing more diverse sources of high grade concentrates, processing and refining capacity. Equally obvious is an over-riding necessity for new technology solutions to combat and eradicate such high level reliance for essential safety orientated applications. Given industrial and urbanisation growth expected in the years to come these are not conflicting objectives for the minerals and chemicals industries to meet.