Mimosa

Overview

Mimosa platinum group metals (PGM) underground mine is located 150 km from Bulawayo in Zimbabwe, Southern Africa.

Aquarius’ 50% interest in Mimosa provides the company with a prime, long-life asset and a foothold on the Great Dyke in Zimbabwe, one of the world’s largest known primary PGM reserves. Implats holds the balance of interest in the mining operation.

The mine, the lowest cost operation in the Aquarius stable, is a relatively shallow underground operation, approximately 200 metres deep.  Mimosa has a well defined grade profile with an identifiable reef horizon marker that facilitates grade control. 

The surface concentrator plant has a monthly processing capacity of 185,000 tonnes. Concentrate produced at Mimosa is transported by road to Implats' Mineral Process in Rustenburg.

Mimosa has a mineral resource of 126.1 million ounces of platinum at a grade of 3.77g/t and an anticipated life-of-mine of at least 40 years. Mimosa has total mineral resources (South Hill and North Hill) of 8.2 million ounces of platinum of which, ore reserves at South Hill account for 1.9 million ounces of platinum.   

Due to an indigenisation requirement in Zimbabwe the owners of Mimosa reached an agreement to sell 10% of operations to workers, 10% to local communities, 6% to State employees, and 25% to a Government fund. (2012)

Location

Mimosa is located on the Wedza Geological Complex on the southern portion of the Great Dyke, some 125 km east of Bulawayo and 30 km from the town of Zvishavane in Zimbabwe. Bulawayo, Zimbabwe's second largest city after the capital Harare, has a population of over 700,000 and is located in the southwestern part of the country.

Zimbabwe is a landlocked country located in southern Africa. Mining agriculture and tourism are the country's largest exports.

Mimosa is a on a well-defined orebody and Mimosa lease encompasses four areas: North Hill, South Hill, Mtshingwe Block and Far South Hill, separated by major faults and covering an area of 6,590 hectares.

Geology and Mineralization

Mimosa is located on the Wedza sub-chamber on the southern portion of the Great Dyke in Zimbabwe. It is an elongated north-northeast-trending intrusion that is 550km long and between 4km and 11km wide. Economic PGE-mineralisation occurs with the Main Sulphide Zone (MSZ) which is lithologically continuous, generally 10m to 50m from the top of the ultramafic sequence and typically 2m to 3m thick.

Although platinum was first discovered in the Great Dyke in 1925, its exploitation was overshadowed by that of the Bushveld Complex inSouth Africa. Focus has returned to the Great Dyke following the increase in demand for platinum and given that much of the shallow resources in the Bushveld Complex are spoken for.

The Great Dyke is a layered complex similar to that of the Bushveld Complex; however, its geometry is elongated overall. It extends for 550km and has a maximum width of 11km, although this does vary. The stratigraphy is broadly divided between the lower ultramafic and the overlying mafic (around 1 100 metres thick) sequences. The ultramafic sequence hosts the P1 pyroxenite, directly below the mafic-ultramafic contact. The P1 pyroxenite, which is marked by significant lateral variations in thickness, texture and composition, hosts the economic PGE-bearing Main Sulphide Zone (MSZ).

The MSZ is a discontinuous PGE-mineralized zone with a potential strike of some 400km and is generally 2-3 metres thick. The optimal mineralization varies and, in contrast to the Bushveld Complex, is often difficult to follow visually. Peak values for the PGM and base metals are commonly offset, while the proportions between platinum and palladium also vary vertically.  

June 2011, mineral reserves at Mimosa were estimated at 31.1 million tonnes grading 3.74 g/t (6E) for 1.7 million ounces of platinum. 

Mining & Operation

The Mimosa mine is a shallow underground mine extending to a depth of 300. The mining method is partially mechanized bord-and-pillar, and is in the process of being converted to fully mechanized. Stoping widths average around 2 metres.

Mimosa achieved record production in 2011 due to improved volumes mined, better grades and higher rates of recovery. Mining performance was positively impacted by the introduction of a revised blasting pattern and retraining of the workforce. Deteriorating ground conditions necessitated upgraded support and safety systems.

In 2011, mining operations produced 2.31 million tonnes ore at 3.63 g/t head grade.

Processing

Mimosa has a concentrator plant on site, where initial processing is done. In terms of a life-of-mine offtake agreement with Impala Refining Services (IRS), concentrate is transported by road to Impala Platinum's Rustenburg Mineral Processes facility in South Africa. 

In 2011, the plant's performance exceeded expectations as a result of the optimisation and improvement initiatives implemented earlier that year. A total of 2.31 million tonnes ore were processed during the year and a total of 219,666 ounces of five platinum group metals plus gold were produced.

Environment & Community

Both management and employees are committed to eliminating injuries and accidents in the workplace, and there is a policy of zero tolerance. A very successful awareness programme concerning falls of ground was launched. Mimosa was awarded a NOSA (National Occupational Safey Association) Five-Star Platinum rating in October 2005.

Mimosa embarked on certification projects for ISO 14001 and OHSAS 18001 to elevate the operations safety, health and environment profiles to international standards.