Cerro Matoso mine
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| Location | |
|---|---|
  Cerro Matoso Location of Cerro Matoso in Colombia | |
| Location | Montelíbano |
| Department | Córdoba |
| Country | Colombia |
| Coordinates | 7°54′18″N 75°33′06″W / 7.9049°N 75.5516°W |
| Production | |
| Products | Nickel |
| Production | 41,000 t (40,000 long tons; 45,000 short tons) |
| Financial year | 2014 |
| Type | Open-pit |
| History | |
| Opened | 1980 |
| Owner | |
| Company | South32 |
| Year of acquisition | 2015 |
The Cerro Matoso mine in northwest of Colombia is one of the largest open-pit ferronickel mines in the world.[1] and the largest mine of South America,[2] containing the largest nickel reserve in Colombia.[1] It is operated by Cerro Matoso S.A., a company that was owned by Hanna Company and the Instituto de Fomento Industrial (IFI), then by Shell, Billiton, and then the Anglo-Australian multinational BHP, since 2015 is owned by South32. There have been allegations that the mine's operations have caused heavy metal pollution affecting especially local indigenous Zenu and Afro-Descendant residents. These allegations have been rejected by Cerro Matoso on the basis of the available scientific and medical evidence. In March 2018 a Review Chamber of the Constitutional Court of Colombia ordered Cerro Matoso to pay damages to local communities. This decision was reversed partially in September 2018 by the Plenary Chamber of the Constitutional Court on the basis that it did not comply with constitutional precedent for payment of damages and noting that there was no evidence of a direct correlation between the mining operations and the alleged damages.
The mine is situated in the northwest of Colombia in the municipality of Montelíbano, Córdoba Department. The deposit was discovered in 1940.[3] It developed over a Cretaceous peridotitic protolith,[3] which is exposed in the form of an isolated elongated hill covering an area of about 4 square kilometres (1.5 sq mi). Ten distinct lithostratigraphic units have been characterized with the highest-grade lateritic nickel ore deposits in the world.[1] The 108 megatonnes (106,000,000 long tons; 119,000,000 short tons) of ore contains 615,000 tonnes (605,000 long tons; 678,000 short tons) of nickel metal.[4]
The hill comprises a holocrystalline rock of fine crystal size. Harzburgites and serpentinized dunites contain between 30 and 90% olivine, replaced by serpentinite.[5]: 11 Two sections through the weathering profile were sampled from an area of the mine with high (pit 1) and lower (pit 2) Ni grades. From bottom to top, the profile in pit 1 is weakly serpentinized peridotitic protolith, saprolitized peridotite, green saprolite (main ore horizon), tachylite (a Fe oxide horizon), black saprolite, yellow and red laterite. The sequence is capped by a magnetic to nonmagnetic ferricrete known locally as "canga". The succession in pit 2 is from serpentinized peridotite, saprolitized peridotite, brown saprolite, yellow and red laterite, and lacks the green saprolite ore horizon. All the units in pit 2 have currently uneconomic Ni grades.[1]
The thickness of the units is highly variable, but most of the major horizons have maximum thicknesses of the order of tens of meters. Both pits contain abundant fault- and joint-related silicate veins. These veins contain the distinctive green mineral known as garnierite (actually pimelite, a form of nickeliferous talc) as well as quartz and chalcedony, and they can have a Ni content of up to 30% to 40%.[1]
Mining
Mining commenced in 1980 at Cerro Matoso and nickel production started in 1982 under the Colombian Government, BHP and Hanna Mining Company ownership.[3]
Nickel production in FY2008 was 41,800 tonnes (41,100 long tons; 46,100 short tons) of contained nickel[1] and in 2014 was 41,000 tonnes (40,000 long tons; 45,000 short tons).[3] In 2017, Colombia was the 11th highest producer of nickel in the world[6]: 112–113 with about 9% of its total mining value coming from nickel.[7]
In May 2015, BHP spun off a new entity called South32[8] for Cerro Matoso and "its non-core businesses".[9]
Reserves
With exploration rights over 77,000 hectares (190,000 acres) in the main part of the Colombian nickel belt, Cerro Matoso has mining concessions containing reserves capable of sustaining the current[when?] level of production for at least 20 years.[1] The mine has an estimated reserve life of 42 years, based on current[when?] production levels. BHP has expanded this significantly by building a third and fourth processing line and a heap leaching operation.[1] BHP Billitons 2008 annual report stated proven ore reserves as under 25 megatonnes (25,000,000 long tons; 28,000,000 short tons), with probable reserves between 25 and 70 megatonnes (25,000,000 and 69,000,000 long tons; 28,000,000 and 77,000,000 short tons).[1] Data acquired by the Colombian mining authority UPME indicated values in 2007 between 21 and 41 megatonnes (21,000,000 and 40,000,000 long tons; 23,000,000 and 45,000,000 short tons).[10] As of 2013 Cerro Matoso had about 108 million tonnes of 0.57% grade ore nickel.[4] The ore reserve has increased as a result of revised price forecasts, reducing the laterite ore cut-off grade used in the reserve estimation from 1.0% Ni to 0.6% Ni.[1]
