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GEMCO Mine

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Overview

Mine TypeOpen Pit
StatusTemporary Suspension
Commodities
  • Manganese
Mining Method
  • Truck & Shovel / Loader
Production Start1964
Mine Life2028
SnapshotGroote Eylandt Mining Company (GEMCO) is an open-cut strip mining operation, producing high-grade manganese ore and is located in close proximity to Asian export markets. It is one of the largest manganese ore producers in the world.

In FY23 South32 approved the Eastern Lease South life extension project, which is expected to extend the mine life at GEMCO, with first ore expected in FY25.

In April 2024, the intense weather system resulted in widespread flooding across Groote Eylandt and significant damage to critical infrastructure, including the wharf and port infrastructure and a haulage road bridge that connects the northern pits of the Western Leases mining area and the processing plant.

South32 said the operational recovery will be focused on re-establishing critical services and dewatering targeted mining pits, but will not be completed until at least 2025.

Owners

SourceSource
CompanyInterestOwnershipInvestor's Info
Anglo American plc. 40 % Indirect
South32 Ltd. 60 % Indirect
Groote Eylandt Mining Company Proprietary Ltd. (operator) 100 % Direct
South32 owns 60 per cent of Groote Eylandt Mining Company Pty Ltd (GEMCO) and Anglo American Plc holds the remaining 40 per cent.

Contractors

ContractorContractDescriptionRef. DateExpirySource
Thiess Pty Ltd. Mining Global mining services provider Thiess has been awarded a three-year contract with GEMCO. The three-year deal, with the potential for a two-year extension, encompasses a range of services critical to GEMCO's manganese operation. Thiess will supply, operate and maintain the equipment for the pre-strip mining operations, as well as undertaking the design and construction of support infrastructure, including workshops and related mobile maintenance facilities. Dec 13, 2023 3

Deposit type

  • Sedimentary

Summary:

Groote Eylandt is dominated by Proterozoic arenites of the Dalumbu Sandstone forming a relatively low-lying plateau on the central and southern portions of the island. Headwater drainage systems incise the quartz-arenites to form radial drainage patterns. The low-lying plains to the north of the plateau are predominantly Mesozoic and Cainozoic strata overlying the Bartalumba Basalts. The majority of the western shoreline consists of the low-lying onlapping Cretaceous sediments which hosts the manganese deposit. The majority of GEMCO’s mining lease area consists of Cretaceous sediments with the exception of a discontinuous narrow strip along the eastern boundary where the Proterozoic sandstone outcrops.

The Groote Eylandt manganese orebody is a sedimentary layer that gently undulates beneath the western plains of the island. It extends over an area of approximately 50 km2 as an almost continuous horizon, varying in thickness up to 11 m and is essentially stratabound and strataform in character. The orebody consists of massive, pisolitic and oolitic manganese oxides. These oxides are thought to have originally been deposited as a chemical precipitate, forming a tabular sedimentary deposit in wave affected shallow sea-floor environments during a period of rising and falling sea levels. Following the deposition and subsequent cover by younger sediments, the western margins emerged from the sea during a worldwide drop in sea level. The depositional events were followed by a long period of tropical weathering which extensively modified the upper parts of the sediment profile. Pisolitic manganese oxides underwent partial to complete remobilisation and recrystallisation that resulted in the formation of hard cemented pisolite and massive manganese oxides.

In the present mining areas, the mined ore horizon is between 0.5 m and 10 m thick. The ‘middle’ mining horizon is typically a massive high-grade cemented ore and loose high-grade pisolite ore whereas the ‘lower’ mining horizon is a massive, high silica ore. The overlying clays and gravels were strongly oxidised and leached to form the laterites that are now excavated off the manganese ore as overburden. In most cases, overburden thickness averages between 15 m and 35 m. The lower part of the sediments below the manganese bearing beds comprise of clayey silt and fine to medium grained sand. Within the sand unit are sections of well-sorted, fine to medium grained marine sand of high transmissivity and storage, which frequently act as aquifers.

Reserves at June 30, 2023

Cut-off grade
Mineral Resources: ROM >35% Mn washed product; Sand Tailings No cut-off grade applied.
Ore Reserves: ROM >40% Mn washed product; Sand Tailings No cut-off grade applied.

Mineral Resources are reported inclusive of Mineral Reserves.
CategoryOre TypeTonnage CommodityGrade
Proven In-Situ (OP) 26 Mt Manganese 42.9 %
Probable Tailings 7 Mt Manganese 40 %
Probable In-Situ (OP) 16 Mt Manganese 42.2 %
Proven & Probable In-Situ (OP) 42 Mt Manganese 42.6 %
Measured In-Situ (OP) 66 Mt Manganese 44.7 %
Indicated Tailings 13 Mt Manganese 20 %
Indicated In-Situ (OP) 35 Mt Manganese 41 %
Inferred In-Situ (OP) 26 Mt Manganese 44.2 %
Total Resource In-Situ (OP) 127 Mt Manganese 43.6 %

Mining Methods

  • Truck & Shovel / Loader

Summary:

GEMCO's existing mining operations include the areas known as the Western and Eastern Leases. The Southern Lease mining project will involve developing an additional mining area that will be integrated with the existing mining operations and will extend the mine life by around three years. GEMCO plans to mine up to 15 million tonnes of manganese ore from the project area, using the same methods as the existing operations.

GEMCO’s operations involve mining manganese ore by open cut mining methods, sizing and washing the ore in the concentrator and transporting the final product to the Milner Bay port facility for shipping.

Mining activities are undertaken over a number of quarry regions simultaneously, with ore profile and composition differing between quarries. Quarry locations are named using alphabetical letters and may be further defined by their geographical location (e.g. B South Quarry). The quarries are typically mined in strips approximately 40 m wide, and generally between 400 m to 1,500 m long. Typical quarry depth varies between 10 and 25 m.

Open cut strip mining involves the following sequence of activities:
• Clearing vegetation using bulldozers.
• Stripping and recovering topsoil. Topsoil is stripped and pushed into windrows, before being picked up by loaders or excavators and placed into haul trucks. The topsoil is then either placed directly on areas that are ready for rehabilitation or temporarily stockpiled in designated areas for later use.
• Pre-stripping overburden. Overburden is excavated in order to gain access to the ore. When commissioning a new quarry, a fleet of excavators and haul trucks is used to remove the overburden. For future strips, the preferred method is dozer push stripping. This material is either temporarily stockpiled or placed directly within previously mined quarries. For routine mining operations, there is no further waste segregation.
• Drilling and blasting the manganese ore. The ore is drilled and blasted to break up the material so it can be easily handled. Mining areas located near Angurugu are not blasted in order to provide a safe stand-off distance from the community.
• Mining ore. A fleet of haul trucks and excavators is used to extract the ore and transport it via a network of dedicated haul roads to the Run of Mine (ROM) stockpile, located at the Primary Crushing Station (PCS).
• Backfilling quarries following ore removal. Dozers are used to backfill quarries with overburden up to the Post Mining Surface (PMS) level to create a stable and free draining landform.
• Topsoil replacement. Topsoil is spread over backfilled areas at an average depth of 0.3 m. The topsoil is then ripped.
• Revegetation of topsoil using seeds from native tree, shrub and grass species using aerial seeding as the primary seeding technique.

Since 2016, mining activities have also included the reclaiming of sands material from existing sands TSFs. This process involves a fleet of haul trucks and excavators to extract the sand tailings and transport it to designated stockpiles located near the concentrator. The processing of this sands material produces a manganese fines product known as PC02.

Ore Stockpiles
Ore is transported from quarries via a network of dedicated haul roads and stockpiled at the ROM located at the PCS. There are a few additional ore stockpiles built outside of the PCS area which generally consist of lower quality ore. Given each quarry has different ore characteristics, stockpiles are built according to the quarry the ore comes from to store ore with similar characteristics. This enables optimised blending of ore for delivery to the concentrator.

Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

  • Wash plant
  • Crush & Screen plant
  • Desliming
  • Vacuum filtration
  • Dense media separation
  • Dewatering
  • Sand Tailing Retreatment (STR)

Summary:

Concentrator
Manganese ore contained within the ROM stockpiles is fed into the concentrator where it is processed to a final product for transport. This process involves the following steps:
• ROM ore is crushed at the PCS and placed on a surge stockpile ahead of the concentrator;
• Crushed ore is fed into the concentrator and washed using a drum scrubber to remove clay components;
• Washed ore is screened into size fractions using vibrating screens. This results in two size fractions of ore (lump and fines) and two size fractions of waste material known as tailings (sands and slimes);
• The lump ore is fed into a rotating drum separator containing a ferrosilicon media. The manganese ore is separated from waste materials (such as quartz and silica) based on density. The ore, being denser, adheres to the ferrosilicon and sinks to the bottom of the separator, enabling it to be removed. The less dense waste materials float to the top and overflow at the discharge end of the drum;
• The fine ore is fed into a series of cyclones which also contain a ferrosilicon media. Similar to the processing of lump ore, the heavier manganese is separated from waste materials based on density;
• Waste material from the rotating drum separator and cyclones is combined to form a course waste material known as middlings, which is stockpiled for later use in operational activities;
• Tailings are separated into the sands and slimes fractions using cyclones. Tailings are then pumped to purpose built TSFs, with the exception of some sands tailings which are pumped to the Sand Beneficiation Plant (SBP) for reprocessing.

The concentrator has a production capacity of approximately 5.2 Mtpa (wet tonnes) of manganese product.

Sand Beneficiation Plant
A SBP, also known as the PC02 plant, was commissioned in May 2016 and runs concurrently to the existing concentrator. The SBP is designed to process up to 2.68 Mtpa (dry) of feed material, producing 0.7 Mtpa (dry) of PC02 product (40% nominal manganese grade). PC02 processing involves the following steps:
• Sands material is reclaimed from an existing sands TSF (TSF feed) or is directed to the SBP from the concentrator (on-line feed);
• Material is screened to remove course reject material (> 2 mm) and fed into a series of reflux classifiers for sizing based on density (similar to the processing of lump and fines ore);
• The product from the reflux classifier is fed onto a horizontal vacuum belt filter for dewatering (to achieve an acceptable moisture level for transport);
• The reject stream (i.e. overflow from reflux classifiers) is pumped into a cyclone to separate slimes from sands. Tailings are then pumped to purpose built TSFs.

Tailings Storage Facilities
The processing of manganese ore results in the production of concentrate products (manganese lump and fines) and waste products (middlings and tailings).

Tailings comprise approximately 45% to 50% of the plant feed and are pumped (via overland pipelines) from the concentrator and PC02 plant to dedicated sands and slimes storage facilities.

Recoveries & Grades:

CommodityParameter202320222021202020192018201720162015
Manganese Head Grade, % 43.844.244.444.645.945.746.247.347.7

Water Supply

Summary:

GEMCO obtains water from four main sources:
• Angurugu River: potable water for use at both the mine and Alyangula township;
• Quarries: groundwater and surface water runoff that collects in quarries for use in processing;
• Rainfall; and
• Rainfall runoff.

GEMCO is well placed to manage variability in rainfall and climatic conditions.

GEMCO has approximately 80 pumps of varying capacity that are used to transfer water across the operation.

The main pipelines on the mine site are for potable water and sewage. Numerous smaller pipelines exist within the concentrator. Portable pipelines are used to move water between quarries, storage areas and the concentrator.

The concentrator has a production capacity of approximately 5.2 Mtpa (wet tonnes) of manganese product and uses approximately 2,250 ML of water per month. The majority of the water used (approximately 65%) is recycled water, returned from the TSFs. Dam 1 is GEMCO’s only purposebuilt water storage facility and it provides the concentrator with the main supply of water for processing. Dam 1 is fed by water dewatered from quarries. On the very rare occasion, a small portion of potable water is also utilised from the Angurugu River under licence.

Production

CommodityUnits2024202320222021202020192018201720162015
Manganese kwmt 5,667 ^5,9085,6055,8825,7835,5825,6604,9905,1184,903
All production numbers are expressed as lump & fines. ^ Guidance / Forecast.

Operational metrics

Metrics202020162015
Annual production capacity 5.2 M wmt of manganese lump & fines5.3 Mt of manganese lump & fines4.8 Mt of manganese lump & fines
Annual processing capacity 9.5 Mt

Production Costs

CommodityUnits20242023202220212020201920182017
Cash costs (sold) Manganese USD 2.15 / dmtu ^   1.88 / dmtu   1.86 / dmtu   1.52 / dmtu   1.55 / dmtu   1.59 / dmtu   1.63 / dmtu   1.52 / dmtu  
^ Guidance / Forecast.

Financials

Units20242023202220212020201920182017
Capital expenditures (planned) M USD 150  
Growth Capital M USD 28  10  
Sustaining costs M USD 68  93  
Capital expenditures M USD 96  103  
Revenue M USD 1,147  1,413  1,141  1,113   1,550   1,473   1,157  
EBIT M USD 443  670  513.3  548.3   980   920   676.7  
EBITDA M USD 615  813  648.3  660   1,072   1,010   760  

Heavy Mobile Equipment

HME TypeModelSizeQuantityRef. DateSource
Dozer Caterpillar D11 18 Oct 1, 2020
Drill Sandvik 1 Mar 16, 2015
Excavator Hitachi EX2500-6 250 t 3 Mar 16, 2015
Loader (FEL) Caterpillar 993K 3 Mar 16, 2015
Truck (haul) Caterpillar 777 95 t 30 Oct 1, 2020

Personnel

Mine Management

Job TitleNamePhoneEmailProfileRef. Date
Engineering Superintendent Matthew W. LinkedIn Jan 3, 2024
Fixed Plant Maintenance Superintendent Wade Watts LinkedIn Jan 3, 2024
Mining Superintendent Ellen Couchman LinkedIn Jan 3, 2024
Procurement Specialist Leonie Costello LinkedIn Jan 3, 2024
Production Planning Superintendent Angus Phelps LinkedIn Jan 3, 2024
Site Manager Iain Jamieson LinkedIn Jan 3, 2024
Superintendent Logistics Filby Robin LinkedIn Jan 3, 2024
Supply Chain Manager Carl Garrick LinkedIn Jan 3, 2024
Technical Services Manager Michael Smith +618-8987-4311 Michael.Smith@south32.net LinkedIn Jan 3, 2024
Technical Services Superintendent John Christowitz LinkedIn Jan 3, 2024
VP Operations Mark Filtness +618-8987-4388 Mark.Filtness@south32.net LinkedIn Jan 3, 2024

EmployeesContractorsTotal WorkforceYear
1,100 2023
1,030 2022
855 212 1,067 2020
1,000 2015
900 2014

Aerial view:

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