Weatherly International Plc Regulatory News (WTI)

Weatherly International plc

('Weatherly' or 'the Company')

Weatherly Decide on Heap Leaching for Tschudi

Weatherly is pleased to announce that based on the results of the preliminary metallurgical testwork, a decision has been made to complete the feasibility study based on a heap leaching processing route. The initial results, while preliminary, confirm previous work carried out by Goldfields in the 1980s and 1990s, and establish a compelling case for the development of a stand-alone heap leach operation. 

The Tschudi project is located approximately 20km due west of the northern Namibian town of Tsumeb and is wholly contained in a granted mining licence (ML125). The orebody, as currently defined, contains a JORC compliant resource of 47.7Mt grading 0.85% Cu and 10.6 g/t Ag (Coffey 2009). The potential open pitable Measured and Indicated resource to a depth of 180m is estimated to contain 25.2Mt grading 0.92% Cu and 10.69g/t Ag (Coffey Mining 2009, as announced 2 November 2009).

As previously announced, Sedgman Limited ('Sedgman') was engaged to manage the feasibility study for Tschudi, which includes supervising the metallurgical testwork conducted by Bureau Veritas - Amdel Limited ('Amdel') and to perform preliminary estimates on potential processing routes.

The Tschudi orebody comprises three discernable ore zones defined as the oxide ore zone, the mixed ore zone and the sulphide ore zone. The dominant minerals in the oxide zone, effectively the top 40m of the ore body, are malachite and azurite. Below the oxide zone there are increasing proportions of secondary sulphides such as chalcocite and covellite hence the designation 'mixed' zone. The oxide component continues to reduce with depth and below 120m the ore mostly comprises secondary sulphides although oxides still persist and some primary sulphides are likely to be present. Subject to the final pit depth, only a small proportion of the mineable resource is contained in the oxide zone (

Preliminary investigations were carried out on two processing routes with the aim of determining which route would most profitably exploit the orebody as a whole. The base case was to acid heap leach all ore types to produce cathode copper utilising a solvent extraction and electro-winning plant (SX/EW). The alternative case was to treat all ore through a conventional flotation plant to produce a copper concentrate. The latter case was introduced as a result of the increasing by-product value of silver which is not recovered in the acid leaching process.

Bulk samples representing each of the ore types were sent to the Amdel's laboratory in Perth, WA and subjected to a series of tests. The heap leach process was simulated by using columns containing crushed ore (13.2mm) and agglomerated fines irrigated with dilute sulphuric acid. Due to the more refractory nature of chalcocite, sulphide ores were pre-cured and inoculated with bacteria prior to leaching.

The results of the initial column leaching tests were as follows:

#1 The oxide and sulphide column leaches are not yet complete and the copper extractions provided are based on the assay heads. Final copper extractions will be determined once the leach residues have been completed.

The company is currently drilling the deposit to obtain a fresh suite of ore samples which will be used to identify any non leachable sulphides occurring within the pit limits and to finalise the heap leach flow sheet. Weatherly will also use the samples to continue flotation work as back up to the base case heap leach study. 

A preliminary evaluation was undertaken by Sedgman based on a 'stand alone' 2 Mtpa open pit utilising heap leach/SX-EW. Based on existing resources, the mine would have a life of at least 10 years and produce (on average) approx. 13,000 tonnes of copper annually. Using costs factored from secondary sources, Sedgman estimated that the capital cost would be approximately US$49m and that the average operating cost would be around US$4,000/t copper, subject of course to final pit depth. 

As well as the detailed design and costing of the heap leach option, the feasibility scope will include a new pit design together with any resulting amendments to the environmental permit which was granted in 2003. Subject to any last minute scope changes, the feasibility study is currently expected to be completed before the end of the year.

Rod Webster said 'The results are better than we expected and fully justify the proposed route which will mean we can produce a final LME grade copper product within Namibia. This will be an important step both in terms of value adding and future employment. Accordingly, we are keen to complete the study and get the project underway as soon as possible'.

For further information, please contact:

Rod Webster, Chief Executive Officer, Weatherly International Plc

+44 (0) 20 7917 2989

Samantha Harrison / Jen Boorer, Ambrian Partners Limited

+44 (0) 20 7634 4700

Carina Corbett, 4C Communications (Investor Relations)

+44 (0) 20 3170 7973