Bisha Mine


Overview

Bisha Mine Location

Bisha is a large, high-grade volcanogenic massive sulphide (VMS) deposit located 150km west of Asmara, Eritrea, East Africa. The Bisha Mine benefits from high grade base metal reserves, strong support of the Government of Eritrea and an advantageous location with good local road and port infrastructure.

The ≈$250 million Bisha Mine was constructed on-time and under budget from 2008 to 2010. Processing oxide ore, the mine produced low-cost gold-silver doré until mid-2013. Through a $110 million copper expansion project, also delivered on time and under budget, throughput expanded to 2.4 Mtpa supergene ore and the product switched to copper concentrate.

Commissioning of the zinc expansion plant commenced in June 2016 and commercial production was declared in October 2016.  The build cost of the plant was approximately US$77 million, compared to a budget of US$100 million.

The Bisha Main deposit is located within the Bisha Mining License and the Harena satellite deposit lies in a separate Mining License 6 kilometers south, connected by a flat unsealed road. Bisha Main and Harena currently make-up 100% of the mineral reserves for Bisha. See the latest presentation for maps and location details.

Click here for details on Resource and Reserves.

The Bisha VMS District remains underexplored and holds strong potential for expanding mineral resources and reserves for the Bisha mill. For more details see the Exploration page.

The State of Eritrea has a 40% interest in the Bisha Mine through the Eritrean National Mining Company (ENAMCO), 30% of which it bought from Nevsun prior to initial construction. As a result, ENAMCO contributed 33% of the initial build capital and, as a partner with Nevsun, has been integral to the success of the Bisha Mine. For more see About Eritrea.

On Nov 22-23, 2016, Nevsun hosted a site visit to Bisha. Presentations given on the visit can be found here.

Bisha Mine and Plant

Bisha is mined using conventional drill and blast open pit mining techniques to remove waste and deliver ore to the run-of-mine (ROM) stockpile. See photo gallery for latest pit and mining operations pictures.

Mined ore is reclaimed from the ROM stockpile and fed to the conventional single stage crushing/SAG/ball mill comminution circuit. The copper and zinc flotation plants are both conventional circuits with rougher, cleaner, and IsaMill regrind. Copper and zinc concentrates are thickened, dewatered and stockpiled prior to land transport to the port of Massawa for shipment to world markets. Tailings are pumped and placed in the lined tailings management facility (TMF) at site.

Power is currently provided to the Bisha plant by a fleet of dedicated diesel generators managed by Aggreko. Nevsun recently signed a long-term power agreement with Aggreko to supply the mine with a combination of diesel and solar power which should be operational by Q4 2017. Water is sourced from pit de-watering, the tailings pond and from local well fields.

Concentrate Export Infrastructure

Concentrate is being exported using a proven system with industry leading environmental controls. At present,concentrate is loaded from the mine site stockpiles into custom sealed shipping containers and transported to the port of Massawa by truck. The sealed containers of approximately 35 tonnes each, including the weight of the container, are stockpiled in Massawa at the container port facilities awaiting bulk ship arrivals. The Rotainer crane system then discharges the containers through a tipping 360 degree rotation into the hold of the bulk vessels and the empty containers are returned to Bisha for re-loading. The bulk vessels deliver the concentrate to smelters worldwide typically in 11,000 tonne parcels.

Resources & Reserves

The Bisha Main deposit is a high grade VMS deposit. It is configured in three distinct layered zones - a 35 meter thick surface gold-silver oxide zone (mined out in mid-2013) immediately overlying a copper enriched supergene zone which itself overlies a primary sulphide zone containing both zinc and copper.

See deposit configuration below.

 

Mineral Reserves (Bisha and Harena)

Effective December 31, 2016

Total Reserves (Proven & Probable)
Tonnes
('000's)
Copper
%
Zinc
%
Gold
g/t
Silver
g/t
Supergene 12 2.57 - 0.71 17
Primary 9,579 1.05 6.16 0.69 45
Total 9,591  

Mineral Reserves are defined within a mine plan, with open pit phase designs guided by Lerchs-Grossmann optimized pit shells, generated using long-term metal prices for copper, zinc, gold, and silver of $2.70/pound, $1.00/pound, $1,200/ounce, and $18.00/ounce respectively.

For more details on reserves, including assumptions, please click here.

Mineral Resources

Effective December 31, 2016*

 

Measured
  Tonnes Copper Zinc Silver Gold
Domain (`000s) (%) (%) (g/t) (g/t)
 
Oxide 10     40 8.4
Supergene 30 2.97   30 0.6
Boundary 10 5.57 1.24 54 0.6
Primary 1,250 1.02 6.62 42 0.8
Total Measured 1,300  
 
Indicated
  Tonnes Copper Zinc Silver Gold
Domain (`000s) (%) (%) (g/t) (g/t)
Supergene 1,130 1.45   10 0.3
Boundary 60 1.34 1.85 24 0.5
Primary 32,480 1 4.24 33 0.5
Total Indicated 33,660  
 
Total Measured and Indicated (including stockpiles) 37,800  
 
Inferred
  Tonnes Copper Zinc Silver Gold
Domain (`000s) (%) (%) (g/t) (g/t)
Oxide 650     19 2.9
Supergene 880 1.19   4 0.4
Primary 28,900 0.99 5.21 31 0.8
Total Inferred 30,430  
 
Total Inferred (including stockpiles) 30,940  

 

For more details on mineral resources, including assumptions, please click here.

A full description of the Bisha mineral resource and metallurgy may be found in the Company's Technical Report.

 

Deposit Configuration

 

 

Technical Report