Gold and uranium
The Ezulwini project involves the re-commissioning of an underground uranium and gold mining operation, located about 40km south-west of Johannesburg, on the outskirts of the town of Westonaria in the province of Gauteng, South Africa. The mine is currently operating on a care and maintenance basis.
The mine was built in the 1960s and eventually reached production of 200,000tpm. In 2001, production at Ezulwini was halted primarily because of capital constraints, compounded by weak gold and uranium prices.
The $280m project is wholly owned by First Uranium through its local subsidiary the Ezulwini Mining Company (Proprietary) Ltd. Existing infrastructure at the site includes two shaft headframes and four hoists, fans, compressors, generators and underground equipment, as well as the necessary surface freehold required to operate the mine.
The capital expenditure for the project had been raised in three ways: through an IPO in December 2006, a convertible debenture in May 2007 and through proceeds from initial production. Payback is calculated at 5.2 years.
In November 2009, Gold Wheaton (GW) acquired the right to obtain seven percent of the life-of-mine gold production from the Ezulwini mine for a consideration of $50m upfront, as well as $400 an ounce upon each delivery.
Gold One International (Gold One) signed a letter of agreement with First Uranium in March 2012 to acquire 100% stake in the Ezulwini Mining Company for $70m (ZAR 539.7m). The assets to be acquired include the Ezulwini gold and uranium mine, gold plant with a rated capacity of 2.4 million tons per annum (mtpa) and a uranium processing facility with a name plate capacity of 1.2mtpa.
The project lies within the Witwatersrand Basin, an Archean (about 2.7 billion years-old) sedimentary basin that contains a stratigraphic sequence about 6km thick, which consists mainly of quartzites and shales with minor intermittent volcanic units. Gold is hosted by the upper Elsburg and middle Elsburg reefs underlying the mine. Uranium is found only in the middle Elsburg reef.
Gold in the upper Elsburg is found in the form of native gold and is associated with sulphide minerals, especially various forms of pyrite. Historically, 30% to 40% of the gold had been recovered by gravity processes, suggesting a high nugget effect.
In the middle Elsburg reef, gold is most commonly associated with pyrite, although some gold occurs in small blebs in arsenopyrite and cobaltite. Uranium is found in the form of uraninite. Mineralisation in the middle Elsburg reef has less of a nugget effect than the upper Elsburg reef.
As of December 2010, the total measured, indicated and inferred resources are just more than 158Mt of about 25Moz contained gold and about 188 million pounds of contained U3O8.
Part of First Uranium’s plans for developing the Ezulwini project had been to rehabilitate and re-engineer the main mine shaft by installing a floating steel tower, de-stressing the area where the shaft pillar intersects the shaft barrel, plus building uranium and gold processing facilities.
The company believes the rectification programme will enable the project to reach a peak production output of about by 2019, as the Upper Elsburg shaft pillar is developed and the Middle Elsburg uranium and gold section stopes are opened and expanded.
The project is a conventional underground mine with breasting of the upper and middle Elsburg reefs. The ore is broken in the stopes and moved by slushers for loading into rail cars for transportation to the shaft.
From the shaft and through the balance of the handling, the gold ores and the gold / uranium ores are kept separate. The ores are then hoisted to the surface for processing.
Ezulwini began gold production in July 2008, with uranium recovery starting in October 2008. Gold production is put at about 288,000 ounces a year while the average U3O8 production is expected to reach 2.1 million pounds a year. The first of two streams of its 100,000tpm uranium plant was operational in the first quarter of 2010. The first container of 23,760 pounds of uranium was shipped in February 2010.
In November 2011, the mining operations were temporarily suspended due to the fall of the ground at the mine. As a result, the production was declined.
The mine produced 59,689oz of gold and 31,407lbs of uranium in 2011. Gold production in 2011 doubled over the previous year, while Uranium declined by 29%. Full production will be attained in 2019 and the mine has an expected life of about 19 years.
The choice of process is based on those previously used on the site. The ore is crushed and ground, then subjected to gold recovery by gravity and cyanidation.
The uranium will be extracted by hot acidic leaching followed by solvent extraction and precipitation to form a concentrate (yellowcake).
The uranium tailings will then be leached for gold recovery. Leaching will occur in a carbon in leach (CIL) process, after which gold will be electrowon and refined into doré bars.
Based on previous operating history, recovery rates of 95.5% for gold and 80% for U3O8 are expected. Water comes from dewatering the mine, which the company says more than meets its needs.
Power comes partly from South African utility Eskom. In June 2008, Eskom agreed to increase its power commitment to Ezulwini from 40MW to 55MW.
But in January 2008, Eskom said it could not guarantee power supplies, so by July 2008, agreements had been finalised to obtain 10MW diesel generators to supplement the power from Eskom and secure a steady supply of owner-generated electrical power, with a total capacity of 24MW, inclusive of 14MW of existing standby units at the mine.
In September 2008, First Uranium struck an exclusive deal with the Traxys Group to market all Ezulwini uranium. The EPCM contractor for the project is MDM Engineering, of South Africa. The value of the contract is about $200m.
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