High-grade, simple orebodies are becoming harder to find, forcing mines to process lower grade and more complex deposits. Being able to quantify the mineralogy of incoming ore-bearing rocks is critical to pre-planning and optimising processing operations as well as controlling costs. Most types of mineral processing activities can benefit from access to accurate daily mineralogy information that is easy to generate, including flotation, leaching, smelting, roasting operations, and others. Recent advances made by Olympus it says now provide even simpler, more cost-effective, real-time quantitative mineralogy for almost any mining operation.

With respect to flotation, using Olympus portable X-ray Diffraction (pXRD) systems, metallurgists, geologists, and mining engineers can quantify problematic and deleterious minerals such as talc and clays that contaminate and downgrade concentrates as well as the proportion of economic minerals that will float (eg sulphides). They can also track changes in alteration to direct oxides to leach pads and sulphides to flotation circuits and better understand tailings rheology for dewatering and environmental reasons.

Looking at leaching projects, metals cannot be leached from all ore-bearing minerals, and ore minerals that can be leached have different leaching potential/leaching rates. In addition, gangue minerals also consume acid during the leaching process. Olympus pXRD can be effectively utilised to estimate recoverable metal, as well as quantify talc and CaCO3 to predict acid consumption, monitor chemical usage and improve process economics. It can also be used to optimise permeability of leach pads and absorption of leach liquor by measuring the content of quartz and swelling clays within leach pads and can help select the most approximate leaching method to optimise value.

Moving on to pyrometallurgy, the mineralogical composition of concentrates has a large impact on subsequent pyrometallurgical processes that can involve smelting and or roasting the mineral concentrate product. Quantitative mineralogy obtained from Olympus pXRD analysers enables metallurgists to optimise their processing conditions, further treat or blend ore prior to smelting as well as classify matte and slag (waste) products.

Taking two mined commodities specifically, in lithium operations, knowing the Li20 concentration is important, but a knowledge of the lithium-bearing phases present (and their quantities) is often more important. Lithium can be easily extracted from some minerals, yet difficult to near impossible to extract from others. With access to quantitative mineralogy, metallurgists can develop more appropriate blending strategies and optimise their processes accordingly. XRD can also be used to identify gangue minerals that can downgrade lithium concentrates. For example, gravity separation is a metallurgical process that can be used to concentrate spodumene. As other non-lithium-bearing pyroxene minerals have a similar specific gravity to spodumene, it is important to identify and quantify other pyroxene minerals.

With iron ore, banded iron deposits are typically made up of magnetite along with partially oxidised iron species such as goethite, limonite, and haematite. All these minerals are processed differently and have different values, so it is important to identify the various species and separate them for processing. High-grade haematite requires only a simple crushing and screening process before being sold to a steel mill, but magnetite needs secondary processing before it can be sold. Goethite and limonite are usually not worth selling because they are difficult to process, and their residue can contaminate the machines.

The presence of magnetite can be determined by measuring the magnetism of the sample, but this method is not generally quantitative and will not identify haematite or goethite. Some operations try to visually estimate the presence of haematite or magnetite, but that method is inexact and prone to error. Olympus pXRD analysers can easily identify and quantify the phases of high-grade and low-grade species as well as the gangue minerals in less than five minutes.

Finally, quantifying minerals that are problematic for metallurgical processes can be far more important than recognising problematic minerals. These problematic gangue minerals often have minimal or manageable adverse effects at or below certain thresholds (or tipping points). For this reason, it is important for the metallurgist to have ready access to accurate quantitative mineralogical data, so they can optimise their process accordingly, or develop more appropriate blending strategies.

Choosing a portable XRD analyser

Olympus says that some considerations to keep in mind when choosing a pXRD analyser are ease of use, required software, and the amount of technical training needed to process the XRD diffraction patterns. Modern pXRD analysers, such as the TERRA™ II battery-operated, field-portable XRD analyser and BTX™ III portable benchtop XRD analyser from Olympus, are powered by SwiftMin® software, which provides an intuitive user interface and improved data export functionality. The company comments: “With this software, there’s no need for a technical expert to process the diffraction pattern data, making the system more productive and cost effective. These instruments use a patented vibrating sample holder that enables the analysers to work with no moving parts or calibration and minimal maintenance. Only 15 mg of sample is required, and only minimal sample prep is needed. Whatever pXRD analyser you choose, carefully consider its portability, ease of use, and functionality to help ensure you purchase the best analyser for your application.”