Successful operations are focussing on mineralogy to improve productivity

A recent article in the Mining News commented that ‘miners have gone from the growth at all costs phase to maximising the productivity of their operations’.

This trend is reflected by the recent increase in comprehensive, ongoing process mineralogy studies being performed by mineralogical service providers, particularly those associated with larger metallurgical testing facilities such as ALS Metallurgy in Balcatta, Western Australia.

What are the benefits?

Operations implementing such mineralogical programmes have confirmed that ongoing monitoring of key process streams via well-designed process mineralogy studies has had a significant impact on their productivity by:

• improving recovery
• improving grade
• lowering risk through better prediction of performance
• accelerating response to changes in the ore
• more rapid troubleshooting
• ensuring focus on continuous improvement strategies

The ability to predict performance of ore through the plant is especially important for operations preparing to move into new ore zones as mining progresses. For example, a gold operation moving from oxide ores, through transition ores, to sulphide ores) or for an operation required to toll treat ore from satellite orebodies. In such cases, the best results are obtained if the mineralogical analyses are done in conjunction with suitably designed, bench scale metallurgical testwork programmes, preferably well before the ore is actually mined!

What streams are being monitored and how?

Composite samples of process streams (generally mill and flotation feeds, final concentrates and tails, and key cleaner and scavenger products) are collected, composited and submitted by the operation on a regular basis. Multiple screen and cyclosizing fractions are generated (either at the plant or at the testing facility) with size fraction limits based on the particle size distribution of the stream in conjunction with assay data.

Assay data are used to validate the mineralogical data and, subsequently, to develop geometallurgical correlations between assay data, mineralogical data and plant performance.

Mineralogical data are generated through a variety of complementary techniques including chemical analyses (usually XRF and ICP), X-ray diffraction analysis, and automated scanning electron microscope techniques which, in the case of the mineralogy section at ALS Metallurgy (Balcatta) includes two QEMSCANs. Various other techniques such as SEM-EDS¹, EPMA² and LA-ICPMS³ are often used during the development stage of the programmes.

For the QEMSCAN analyses, the products are mounted in a two-part liquid epoxy which, when hardened and polished, provides a two-dimensional cross section through a representative population of particles. These particles are then mapped at an appropriate analysis point spacing to provide maps from which a variety of quantitative parameters can be extracted.

One of the strengths of the service provided by the mineralogy section at ALS Metallurgy (Balcatta) is in the data presentation. Customised spreadsheets are developed in collaboration with the plant metallurgists with data from progressive months continually added to the existing data, building up a database that can be monitored and compared to plant performance parameters.

Data generally includes a combination of tables, graphs, image grids and particle maps. Apart from being readily reviewed, this form this data is a powerful communication tool during team discussions.

Data output is customised for each client and can include:

• Bulk modal mineralogy
• Elemental deportment
• Grain size and particle size distribution data
• Mineral association data
• Mineral liberation and locking analysis
• Theoretical grade-recovery curves
• Theoretical density data

What commodities are being monitored?

Ongoing mineralogy studies benefit operations processing all types of commodities and minerals but are especially relevant to those with complex ore types or highly variable mineralization. The team at ALS Metallurgy (Balcatta) have extensive experience in a large number of commodities including:

• Base metal ores including copper, cobalt, lead, zinc, molybdenum
• Nickel – lateritic and sulphide ores
• Rare Earth Minerals
• Precious metals – gold, silver, Platinum Group Metals
• Uranium ores
• Iron ore – magnetite, hematite, goethite, limonite
• Manganese ores
• Mineral sands
• Bauxite ores
• Tungsten and tin ores
• Industrial minerals

The most important consideration!

Ultimately, the responsibility of data interpretation including integration with other operational parameters, and making appropriate adjustments to plant operation, reverts to plant personnel. Adequate communication between key personnel at the plant and at the service provider is therefore critical to ensure that the entire programme, from sampling to data presentation, focuses on the desired goals.

¹ SEM-EDS = scanning electron microscopy using energy dispersive spectrometry

² EPMA = electron probe microanalysis

³ LA-ICPMS = laser ablation using inductively coupled plasma mass spectrometry