(Silver Standard 2013). The mine has a low cost base, principally because of the leaching
recovery technique employed. Should Pirquitas recover the indium, we estimate that it would be
an overall low cost producer at ~$160/kg in 2011 USD.
Doe Run Peru, a wholly owned subsidiary of the U.S. company Renco Doe Run, is a mining and
metallurgical company with operations located in the central highlands of Peru. The company
has owned the La Oroya Metallurgical Complex since October 1997 and the Cobriza mine in
Huancavelica since September 1998.
Doe Run Peru processes concentrates from third parties, most of which are Peruvian. The smelter
and refineries of La Oroya extract and recover copper, zinc, silver, lead, indium, bismuth, gold,
selenium, tellurium, and antimony, among others. The La Oroya Metallurgical Complex has the
capacity to produce up to 6 tpa of 4N1 quality indium. The company also produces tellurium of
99.94% (3N4) purity at La Oroya (Doe Run Peru 2012).
South Crofty is a metalliferous underground tin and copper mine located in the village of Pool.
The mine has a long history and evidence of mining activity dating back to 1592; full-scale
mining began in the mid-17th century. The mine extends almost 2 ½ miles across and 3,000 feet
deep and mining has occurred in more than 40 different lodes
tin in 1985 and subsequent knock-on effects on viability caused it to decline after 1985 and to
eventually close in 1998. The mine still possesses significant resources of tin, copper, and zinc.
Mineralization at South Crofty is in the form of lodes that occur within fracture zones and
generally trend east-northeast to west-southwest. The lodes display a general moderate to steep
dip to the southeast. Occasional opposite, moderate to steep dipping lodes are present in the
system. A summary of the in situ classified inferred resource for the project, using a tin
equivalent economic cutoff of 0.30%, is estimated at approximately 1.331 million inferred
tonnes of 0.44% tin, 1.08% copper, and 0.66% zinc. Although not forming part of the formal
resource classification, total indium contained within the “potential resource” estimated in early
2011 for internal planning purposes and summarized in Table 17 is 85 tonnes, with an average
grade of ~36 ppm.
Data for the South Crofty mine are preliminary. Conceptual mine planning and a preliminary
economic assessment have not been performed. For internal planning purposes, Celeste Copper
Corporation, which in 2011 and 2012 evaluated possibly reopening the mine, stated that total
costs could be ~$50/tonne mined by underground mining techniques, potentially through Alimak
In geology, a lode refers to a rich accumulation of minerals in solid rock, frequently in the form of a vein, layer, or an area with
South Crofty Dolcoath—Potential Metal Content in Resource
Wireframe Zone Name
Dolcoath South Branch
The potential resource described above is not JORC
or NI 43-101 compliant, but produced to give an indication
of the potential resource.
The weighted average concentration of indium in the potential mineral resource is 36.7 ppm.
Additional exploration potential of ~5 million tonnes occurs at similar indium and other metal concentrations.
To provide indicative results, we assume (1) an overall indium recovery rate of 80% at the
from similar scale operations; (4) sustaining capital equivalent to 10% of total operating costs;
and (5) a contingency of 30% on all costs. With these assumptions, we calculate that 10 tpd of
refined indium could be produced at a total cost of $342/kg. Because dialogue with the nearby
community is ongoing and the mine’s reopening is uncertain, we do not believe that production
could commence until 2017 at the earliest.
Recovery yields are another important contributor to increased outputs. In the medium term,
higher indium prices make it economically viable for mines, smelters, and refineries to invest in
increasing yields and capacities.
A study undertaken by Indium Corp. shows that only approximately 30% of the total indium
mined worldwide every year is transformed into refined indium metal (Mikolajczak 2009). Our
calculations put the overall recovery closer to 15%–20%, and as depicted in Figure 18, the major
causes of the low overall recovery rate are:
Based on the process described for zinc ore mined, only 50%–70% of the indium
Of these indium-pregnant zinc concentrates, 30% are not sent to “indium-capable”
The indium in the remaining indium-pregnant concentrates that are sent to indium-
The impure indium is sent for advanced refining at various special metal refineries where
JORC is the Australasian Joint Ore Reserves Committee. The JORC committee produces the JORC code, which is the