22
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications
•
Based on the process described for zinc mining and processing, only 50%–70% of the
indium contained in the ores is recovered by the on-mine treatment plant and report to the
zinc concentrate.
•
Of these indium-pregnant zinc concentrates, 30% are not sent to indium-capable smelters
(Mikolajczak 2009) and are lost to smelter tailings or slag heaps.
•
The indium in the remaining indium-pregnant concentrates that sent to indium-capable
smelters is recovered at an average rate of ~50% in an impure form (Mikolajczak 2009),
such as a sponge.
•
The impure indium is sent for advanced refining at various special metal refineries where
the recovery rate averages ~80%.
Zinc ore
100 units indium
Zinc concentrate
50–70 units indium
50-70%
Mine tailing
30–50 units indium
30-50%
Non-indium capable
smelter
15–21 units indium
30%
Indium-capable
smelter
35–49 units indium
70%
Smelter waste
18–25 units indium
Refinery
18–25 units indium
50%
50%
Refinery waste
4–5 units indium
20%
Indium (+99.97%)
14–20 units indium
80%
For every 100 units of indium metal mined along with zinc ores, only ~15–20 units is recovered as refined metal.
Figure 10. Indium value chain and overall recovery efficiency
(Schwarz-Schampera and Herzig 2002; Mikolajczak 2009)
Heath Steele reports that 35.8% of indium in ore is reported to tailings and 51.4% went to zinc tailings (Schwarz-
Schampera and Herzig 2002).
Brunswick 6 and 12 mills reportedly recovered only 58.9% of the indium in zinc concentrate (Schwarz-Schampera
and Herzig 2002).
At Toyoha, the recovery of indium in zinc concentrates was ~96% (same as estimated for zinc recovery in zinc
concentrate). This mine was a main product indium producer, so these high recoveries are unlikely to be
representative of byproduct indium producers.
Indium recovery in mine concentrates is ~50%–70%.
As detailed above, the cumulative effect of these losses results in only 15%–20% of mined
indium being recovered. This suggests at least one explanation for the mismatch between our
estimates of mined indium and those for refined metal production. Given the low overall
recovery efficiency and cumulative losses of indium throughout the value chain, the figures for
total mined indium production presented in Table 3 (629 tonnes in 2013) could be significantly
underestimated.
The data on indium demand as well as primary refined indium provide useful benchmarks and
support an estimate of primary refined metal of 640–822 tonnes. Furthermore, various sources
tend to confirm an overall recovery efficiency of 15%–30%. With this in mind, and assuming
that the overall indium recovery efficiency corresponding with zinc ores is similar to those of
other main product ores, the total potential tonnes of indium mined in 2011 could be 2,130–5,870
tonnes, as tabulated in Table 8. The upper end of this range is almost an order of magnitude
23
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greater than the estimate of 615 tonnes when using a methodology adopted by Roskill (2010).
21
Because the data on indium content in base metals ores are (according to Roskill’s own
admission) highly uncertain, and because we have more data points and confidence in our
estimates of overall recovery efficiency and levels of primary refined indium production, we
believe the mined indium estimate to more likely be ~5,200 tpa, coinciding with the midpoint of
the high scenario identified in Table 8. We use this figure in subsequent calculations.
Table 8. Estimates of Potential Indium Mined Along With Main Product Ores
USGS
Own Estimates
Midpoint
Refined metal production (tpa)
640
822
730
Corresponding potential tonnes of contained indium mined per annum (tpa)
a
Low
b
2,133
2,740
2,437
Med
b
3,265
4,194
3,730
High
b
4,571
5,871
5,221
Range
2,133 to 5,871 tpa
5,221
a
Estimates of potential indium mined per annum are calculated as follows: tonnes mined per annum = refined metal
produced/overall recovery efficiencies.
b
The corresponding recovery efficiencies for low, mid, and high estimates of tonnes indium mined are 30%, 20%,
and 14%, respectively.
Sources: Own estimates; Mikolajczak (2009); USGS estimates (i.e., Tolcin 2011a and 2012a)
3.6 Summary of Primary Production
As noted in Table 8, total global production of primary refined indium metal in 2013 was 770
tonnes. In recent years primary indium production was ~640–822 tpa. China is the largest
producer of refined indium with ~50%–55% of global production. The remaining 45%–50% of
primary indium production is distributed among countries such as Belgium Canada, Japan, and
South Korea.
An analysis of overall indium recoveries has shown that significant losses of 70%–85% occur
throughout the value chain, representing a significant opportunity for increasing indium supply
in the short to medium term.
Until now, we have focused on summarizing existing supply characteristics of primary indium.
We now turn to estimating a supply curve for current indium production, which involves not
only estimates of indium quantities but the price at which indium can be produced. As is often
the case with mineral properties, the best and most detailed information available for costs and
efficiencies is contained in technical reports filed with the securities exchanges by midsized and
junior mining companies as part of their disclosure requirements.
22
Information in these reports
can then be used together with the distribution of indium concentration in currently known
21
This methodology is incompatible with the methodology adopted by Roskill, because recovery of indium from ores efficiency
would need to be greater than 100%. Alternatively, a significant amount of primary indium would have to be produced from non-
mined sources, which represents an unlikely scenario.
22
Often, large mining companies are not required to disclose detailed technical information about development projects or
ongoing operations, because the performance of a single operation is, in many cases, not significant to the overall value of the
company.