Combining these estimates with the information from Table 1 yields total world mine production
of indium of ~550 and ~700 tonnes in 2009 and 2013, respectively.
The methodology adopted herein to estimate total indium mined along with main product metals
is highly subjective and is likely conservative.
3.4 Smelting and Refining
Indium is recovered from mine concentrates or from dusts and residues produced during
smelting. It is then typically refined to a purity of 99.99% (known as 4N or four “nines”) and
sent to a special metals refinery/plant and further refined to 6N or 7N purity, or manufactured
into products such as ITOs, alloys, and compounds.
Few companies operate fully integrated indium recovery and refining facilities. Roskill (2010)
identifies the following rare exceptions:
Japan Energy Corp., the largest integrated indium producer in the world. It is a
the merger of Nippon Oil Corporation and Nippon Mining Holdings, Inc.
Canada’s Teck Resources Limited (Teck). Teck produces copper, coal, zinc, lead, and
such as indium and tellurium as byproducts. A key operation is its integrated smelting
and refining complex at Trail in British Columbia, Canada, where its main products are
refined zinc and lead; indium is a byproduct.
Chinese state-owned Hunan Nonferrous Metals Corporation Limited, a large
nonferrous metals. It operates in three segments: (1) nonferrous metal mining; (2)
nonferrous metal smelting; and (3) their compounds production.
Most indium producers are not fully integrated. A number of mining companies never recover
refined metals at their own facilities and simply sell indium-bearing concentrates on the open
market. Prospective buyers of zinc concentrates (and associated indium impurities) can be
grouped into three major categories: commodity traders, smelters, and manufacturers of zinc
The main differences between these categories relate to the allocation of
Smelters typically offer two options for processing concentrates:
1. Toll processing, where a company (which has specialized equipment) arranges to process
the zinc concentrate on behalf of the owner of the concentrate. In this case, the owner of
the concentrate has a set percentage (net smelter return) of the refined zinc produced by
the smelter for which it is responsible for marketing and shipping to end users after
processing (Thibault et al. 2010).
2. Alternatively, the miner can directly sell the zinc and indium contained in concentrates to
the smelter and the smelter in turn sells the refined zinc to end users (Thibault et al 2010).
Steel industry, brass manufacturers, and the die-casting industry, for example.
Table 4 includes a non-exhaustive list of well-established prospective buyers for indium-bearing
Table 4. List of Prospective Buyers for Indium-Bearing Zinc Concentrates
Teck Resources (Canada)
Amalgamated Metal Corporation (AMC)
Trading Group (Worldwide)
Chelyabinsk Zinc (Russia)
Glencore International AG (Worldwide)
Laibin Smeltery (China)
Euromin SA/Vitol (Worldwide)
Dowa Mining (Japan)
ANI Metal and Chemicals (Turkey)
Korea Zinc (South Korea)
Ocean Partners (United States)
Lundin Mining (Portugal)
Mitsui Mining (Peru)
Marco International (United States)
Source: Thibault et al. 2010
refineries. To produce a metal that is high enough quality to be accepted by specialist refiners,
these companies need to produce a high quality (+95% purity) indium at either the mine site or at
their own smelting facilities. As an example, before its closure in May 2010, Xstrata (formerly
Falconbridge Ltd.) produced indium at its Kidd Creek zinc-copper mining and refining division
at Timmins, Ontario. 3N indium (99.9%) was produced at a refining plant built as a joint venture
with Indium Corp., and the indium was shipped to Indium Corp.’s facilities in New York where
it was refined to 4N grade (99.99%) or higher.
Not all indium that enters a zinc (or other metals) smelter is recovered. Once the indium has
entered the smelting process there are three principal channels: (1) indium is discarded by the
either because the smelter lacks indium recovering capabilities or as normal
smelter and then sold to a third party refinery where it can be upgraded to commercial-grade
indium; or (3) indium is recovered by the smelter and then refined to commercial grade in its
own special metals processing refinery.
Where indium is a byproduct of zinc smelting, it is normally sold as a sponge. The typical
minimum purity of indium in the sponge required by refineries is 95% where certain impurities
may attract a penalty.
refineries from fumes, dusts, slags, residues, and alloys from zinc, lead-zinc, or lead-tin-zinc
The solutions are concentrated and crude indium is recovered as low-grade 99%
purity grade (99.999% [5N]), or to grades up to 99.99999% (7N), and can then be produced in
Approximately 30% of indium-bearing concentrates are not sent to indium-capable smelters (EU 2010a; Mikolajczak 2009).
Typical impurities associated with the indium sponge that may attract a penalty charge by the refinery are arsenic, cadmium,
thallium, lead, tin, and copper. As a result, care is normally taken in designing recovery processes to ensure that these impurities
are extracted prior to the formation of a sponge.
Normally these materials (as well as the slag) are leached with sulfuric or hydrochloric acid for indium recovery.