South Africa

Masimong Mine

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Overview

Mine TypeUnderground
Commodities
  • Gold
Mining Method
  • Undercut mining
  • Conventional narrow-reef mining
Production Start... Lock
Mine Life2025
ShapshotMasimong is a deep-level mine in the Free State. The operation is close to the end of its mine life. The Masimong complex comprises two shafts with 5 shaft used as the operating shaft and 4 shaft for ventilation, pumping and a second escape outlet. Ore mined is processed at the nearby Harmony One plant.

Owners

SourceSource
CompanyInterestOwnership
Harmony Gold Mining Company Ltd. (operator) 100 % Indirect
Harmony has Masimong underground mining operation.

Contractors

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Deposit type

  • Conglomerate hosted

Summary:

Mining takes place in a structurally complex zone between two major north-south trending faults: the De Bron/Homestead Fault in the west and the Saaiplaas Fault in the east. The orebody has been subjected to severe deformation and contains numerous folds (anticlines and synclines) as well as an abundance of smaller faults. The dip of the reef bands is very variable – from 45 degrees to the east, adjacent to the western side of the lease, to less than two degrees in parts of the southern area.

Production is hosted within two quartz pebble conglomerate bodies, developed above unconformity surfaces, the Basal and the B reefs. Approximately 80% of the centares (1 centare = 1 square metre) are from the Basal Reef horizon and 20% from the Basal B Reef horizon.

The primary facies of Basal Reef intersected at Masimong 5 Mine is the Black Chert facies. It comprises two upward fining cycles. The lower one has a small to medium pebble conglomerate at its base, overlain by a grey ortho-quartzite. The upper unit consists of a pyrite-rich grit. The upper cycle tends to erode large segments of the Lower higher grade cycle in the south-west, with resultant lower values. Towards the east of the shaft, it appears that only the upper unit is present. Carbon is almost always present on the bottom contact of the lower cycle of the black chert facies.

The B3 facies of the B-Reef comprises polymictic medium to large pebble-supported conglomerates, with porphyry clasts, and yellow and green shale pebbles (fragments). The shale clasts are angular and tabular with the most common being yellow to mustard in colour. The non-durables account for 5-10% of the total clast composition. The durable pebbles are mainly black, smoky and vein quartz, sub rounded to rounded. Pebble sizes range from 0.7-4.5cm, and are poorly sorted. The matrix has a yellow-green argillaceous composition with noticeable yellow and black speckling. The B3 can occur on the shale or above the B2 quartzite. It can be a solid band or inter-bedded. The B3 facies is the primary facies being mined at Masimong and range from a pebbly quartzite to matrix or clast supported conglomerate with carbon present in the latter.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Summary:

Ore Reception:
The use of parallel processing starts at the ore receive bin, where there are two unloading stations for the railcars that bring the ore in from the various shafts and rock dumps. A unique feature of the Plant is the Ore Reception facility, which has been designed to eliminate dead storage space, a serious constraint in railway ore storage bins. Ore is transported by rail to the Plant. The railway hoppers discharge individually into one of the two concrete, rail-lined inverted cones, 12m in diameter and 8m deep. The apex of the cone is 57o. The ore is rapidly withdrawn from the apex of the cone via a shuttle belt feed conveyor feeding onto a main silo feed conveyor. The twelve ore storage silos are constructed from concrete and are also rail-lined. Each silo has a live storage of approximately 3 000 tons. Ore is discharged onto the mill feed conveyor via a pneumatically-operated Langlaagte chute. When filled to full capacity, the twelve ore silos provide approximately 60 hours storage for the six Run-of-Mine (ROM) mills.

There are six parallel and independent milling lines with each one having a conveyor running underneath 2 silos (A and B) and taking the ore up into one of the six run-ofmine (ROM) mills. Generally, ore is drawn only from one of the two silos for each mill whilst the other is being filled with ore. Hence, one silo is discharging onto the mill feed belt, and the other refilled.

Milling:
The ore is taken up the slow-moving conveyers from underneath the silos and discharged directly into the feed hopper for the ROM (Run Of Mine) mills. Fully autogenous (FAG) milling is a milling process in which the entire ROM ore stream is fed directly into the mills. The grinding media is generated within the mill from suitably sized pieces of ROM ore itself, supplemented by waste rock dump material. The feed rate to the mills is between 90 and a 100t/h.

The milling circuit consists of six single stage ROM mills that are controlled on maximum power, utilising programmable logic controllers (PLCs). Variations in mill load are measured by load cells situated under the outlet trunnion bearings. Each ROM mill is 4.9m diameter by 10m long and powered by 3.3MW motors and grinds the ore to between 68 and 73% minus 75µm.

For control purposes, the mill feed belts and the mill discharge pumps both have variable speed drives. Each mill is in closed circuit with a 1200mm primary cyclone with mass flow measurement on the feed. The primary cyclone overflow is screened on a 600µm linear screen for the removal of coarse woodchips and tramp steel. This has the purpose of preventing gold losses and carbon contamination in the downstream CIP circuit. Cyclone overflow, which has a low density, is pumped out to the thickeners. The current cyclone overflow size is 68% at -75µm.

Processing

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Production

CommodityUnits2024202320222021202020192018
Gold oz 0000000000000000000000000000000000084,332
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.

Operational metrics

Metrics202320222021202020192018
Tonnes milled 000000000000000647 kt

Production Costs

CommodityUnits202320222021202020192018
Cash costs Gold USD 0000 0000 0000 0000 1,153 / oz   1,071 / oz  
All-in sustaining costs (sold) Gold USD 0000 0000 0000 0000 1,302 / oz   1,242 / oz  

Operating Costs

Currency20172016
Total operating costs ($/t milled) USD 116  100  

Financials

Units2024202320222021202020192018
Capital expenditures (planned) M USD  ....  Subscribe
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Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 117  
Gross profit M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 27  

Heavy Mobile Equipment

Fleet data has not been reported.

Personnel

Mine Management

Source Source
Job TitleNamePhoneEmailProfileRef. Date
....................... Subscription required ....................... Subscription required ........... Subscription required ........... Subscription required Subscription required Nov 7, 2023
....................... Subscription required ....................... Subscription required Subscription required Nov 7, 2023

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2023
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Aerial view:

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