Conflict Minerals and the Tin Supply Chain: Where the World's Tin Is Smelted

The U.S. Geological Survey analyses supply chains for minerals and metals, following them from the mine through intermediate forms to finished products. Such analyses can reveal risks to the U.S. supply of critical and strategic minerals and give policymakers the facts they need. This fact sheet covers the stretch of the tin supply chain after mining and before consumer products.

Why tin — and why smelters

Government and non-government organisations asked the USGS National Minerals Information Center for information on facilities around the world that process tantalum, tin, tungsten and gold — the "3TG" minerals — in response to U.S. legislation aimed at identifying and breaking the links between trade in these minerals and civil unrest in the Democratic Republic of the Congo (DRC) and neighbouring countries.

Company and industry representatives identified the processing plants after ore concentration — usually called smelters and refineries — as the link in the chain where these minerals can be traced back to the mine they came from. Knowing that origin is essential to a complete, transparent, conflict-free supply chain. This is the third fact sheet in the series, after tungsten (August 2014) and tantalum (December 2014). It lists selected plants that produced tin commercially in 2013–14; it gives no information on where their raw material came from.

Tin and where it is mined

Tin usually occurs in nature oxidised, as the mineral cassiterite, which has always been, and still is, the main source of tin; small amounts also come from sulfide minerals such as stannite. Cassiterite is found in alluvial deposits and in lode deposits with other metals. In 2014 the leading producers of tin concentrates were, in order, China, Indonesia, Peru, Bolivia, Brazil and Burma. China and Indonesia supply more than 60 percent of the world's tin; the DRC and its neighbours only 3 percent. The DRC's deposits are thought to be large, but its mining is not developed enough to make a noticeable difference to world production.

Share of world tin mine production by country, average of 2009–13, and the countries with primary tin smelters in 2013. China had 42 percent; the DRC 2 percent. USGS.

In the DRC, tin is mined mostly by artisanal methods, in Katanga, Maniema, Nord-Kivu and Sud-Kivu Provinces; most of the rest of the region's tin comes from Rwanda, also by artisanal mining. There are no estimates of the region's tin reserves, but they are believed to be large, the biggest in the Kivu region.

• In January 2015 a new smelter in Rwanda, run by Phoenix Metals Ltd. and reported to have a capacity of 2,200 metric tons of tin a year, began a 10-day pilot run; its owners were seeking conflict-free certification, with the final audit expected in July 2015.
• By May 2015 the Lubumbashi smelter in the DRC, able to produce 3,600 tons a year, had reportedly reopened after closing because of an unreliable power supply.

From ore to metal

1. Mining. Alluvial cassiterite is dredged, the ore broken up by high-pressure water or an excavator; hard-rock ore is usually mined underground.
2. Concentrating, usually at the mine, by flotation, gravity and magnetic methods, gives a concentrate of 70–77 percent tin.
3. Smelting. The concentrate is heated with carbon to 1,200–1,300 °C, reducing the cassiterite to tin metal and giving off carbon dioxide.
4. Refining, usually next to the smelter, removes the remaining impurities: impure tin is heated just above its melting point so the impurities drop out as solids and the pure liquid tin can be skimmed off. The slag can contain tantalum, another conflict mineral. Heat treatment in a fuel-fired reverberatory furnace is the more common method and gives 99.85 percent tin; electrolytic processing, which heats the concentrate by passing electricity through it, costs more but gives up to 99.9999 percent tin.

What tin is used for

Tin is the main ingredient of solder, the fusible alloy that joins two pieces of metal and, in electrical work, carries current across the joint. It coats steel to make tin plate for food cans. Organotin chemicals stabilise PVC during manufacture, preventing heat damage and the release of hydrogen chloride. Tin also goes into bronze and brass, into babbitt, a low-friction metal used in engines, and into terne metal, a rust-inhibiting coating for metal roofs.

Who smelts it

More than 25 primary tin smelters were part of the world's supply chain in 2013. The fact sheet's table lists smelters and refineries in Australia, Belgium, Bolivia, Brazil, China, the DRC, Indonesia (the most entries, chiefly in Bangka Belitung Province), Malaysia, Peru, Rwanda, Thailand and Vietnam; more small smelters may be operating in Indonesia.

The USGS lacks full data on these plants' raw materials and methods, so it cannot say whether they used tin concentrates or where those came from; some may use recycled tin, tin slag, scrap or intermediate products. Plants known to process only recycled material, and small Indonesian plants tied to artisanal mining that cannot handle imports, were left out. The information came from company reports, governments, analysts, industry and intergovernmental bodies, NGOs and trade journals, with names and locations checked against company websites. Some suppliers could not be confirmed, because companies had changed names or owners, been referred to loosely, or gone out of business.

How tin moves around the world

From 2011 to 2013, China, Malaysia and Indonesia dominated the supply chain: they produced 63 percent of the world's tin ores and concentrates, imported 95 percent of them, and accounted for 95 percent of primary smelter output, which averaged about 300,000 tons a year. The DRC and its neighbours produced only 3 percent of mined tin. According to the United Nations Comtrade database, the leading importers of DRC tin ores and concentrates in those years were China (53 percent), Malaysia (39 percent) and Rwanda (7 percent).

• China is both a major producer and a major consumer. Its imports were about 59 percent of reported world imports of tin ores and concentrates, from Burma, Bolivia and Tanzania. It was not a leading exporter of tin and tin articles, and imported about 6 percent of world exports of them, from Malaysia and Indonesia.
• Malaysia, with less mining of its own, imported about 33 percent of the world's tin ores and concentrates, from Australia, Rwanda and Nigeria, and supplied 12 percent of world exports of tin and tin articles — mainly to the Republic of Korea (19 percent), India (14 percent) and China (13 percent).
• Indonesia produced 20 percent of the world's tin ores and concentrates and supplied 28 percent of exports of tin and tin articles, shipped mostly through Singapore to China, Malaysia and the Netherlands.

Secondary producers, who make tin products from recycled material, are an important part of the chain but are not covered here.

The fact sheet says China imported 157.8 million metric tons of tin ores and concentrates in 2011–13, a figure out of scale with world smelter output of about 300,000 tons a year; this page leaves the tonnage out.

Sources

• U.S. Geological Survey, National Minerals Information Center, Conflict Minerals from the Democratic Republic of the Congo—Tin Processing Plants, a Critical Part of the Tin Supply Chain, Fact Sheet 2015–3022, version 2.1. https://doi.org/10.3133/fs20153022