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:: Mintek Expands Analytical Facilities
Mintek, South Africa's national minerals research organisation, has expanded its precious-metal assaying facilities in response to the increasing demand for analytical work on geological exploration samples, particularly from new platinum-group metal (PGM) projects.
A new 75 kW fusion furnace has been installed in the fire-assay section, bringing the total number of fusion furnaces to five, while the number of cupellation/muffle furnaces has been increased to six with the addition of two new 30 kW units. The new equipment has effectively doubled the Analytical Services Division's fire-assay capacity from 1000 to around 2000 samples per month.
Fire assay is the oldest, and in most circumstances still the best, technique for the determination of precious metals. The finely ground sample is fused with a suitable flux under reducing conditions, which promotes the separation of precious metals from the gangue. The precious metals are simultaneously collected - normally in a lead alloy or nickel sulphide button.
For the determination of total gold or total PGMs plus gold, fire assay is followed by a gravimetric finish. Where determinations of the individual metals are required, the button containing the precious metals is dissolved and the solution analysed by trace ICP-OES. This technique can detect individual PGMs at concentrations down to 0.1 ppm. In mid-2003, Mintek acquired a new Perkin-Elmer Optima 4300 instrument, which complements the existing Optima 3300 and has increased sample throughput from 100 to 200 each shift.
A dedicated sample-preparation facility for crushing and pulverising borehole-core and other geological samples has also been installed. Mintek's analytical facilities also play an important role during major pilot plant campaigns carried out to develop or verify circuit design criteria for bankable feasibility studies. By speeding up the turnaround of analytical results, the new facilities will support improved decision-making during these campaigns.
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