6 Precious metal analysis methods using advanced analytical technologies

Finding, excavating, and processing metals like gold, silver, and platinum group metals (PGMs) presents unique challenges. These metals are intrinsically valuable because they are rare – but even if they were as common as sand, they would still be valuable due to the critical roles they play in electronics, medical devices, and many other applications.

As a result, few industries are as focused on innovation to improve efficiency. After all, when dealing with such precious commodities, even a 1% improvement in recovery rates can mean millions of dollars in additional profits.

Read on to learn about 6 precious metal analysis techniques that, when combined, enable more informed, data-driven decision-making, improving productivity, yield, and profit. But first – what obstacles stand in the way of these improvements?

What are the challenges in precious metals mining?

Analytical technologies improve precious metals mining by addressing numerous challenges related to exploration, operation, and process optimization. When prospectors, miners, and process operators have a comprehensive understanding of ore deposits and excavated materials, they can locate, dig, and recover specific metals far more efficiently.

These are the key difficulties facing precious metals mining right now.

Less easily detectable ore deposits

Over the last few decades, precious metals exploration has become more difficult due to the depletion of easily detectable ore deposits. Advanced prospecting and exploration technologies – for instance, NIR spectroscopy – help mining companies detect ores even in lower concentrations.

Increasingly remote mines

As ore deposits become more remote, it becomes increasingly important for each measurement to be transmitted and usable by operators at each step of the mining process, regardless of distance or operator skill. Advanced precious metals analysis can offer improved connectivity between instruments.

Process optimization

By enhancing connectivity, operators and autonomous machines – whether drilling robots or automated ore sorting equipment – can use more complete and insightful data to optimize processes even further.

Avoiding effects such as preg-robbing

Finally, advanced analysis can help mining companies avoid complications that could sabotage their yield, for instance, the phenomenon of preg-robbing.

Preg-robbing refers to a process whereby recoverable gold is lost during processing, when the gold attaches to carbonaceous materials in its ores instead of staying in solution. It cannot be reversed and is therefore important for gold mining companies to mitigate.

Precious metals analysis is instrumental in helping mining companies avoid preg-robbing. It gives operators insight into particle size and surface area – both of which are key factors in preg-robbing risk – and adjusting their pre-processing to compensate.

With these issues in mind, which precious metals analysis methods should mining companies focus on to improve productivity, yield, and profit?

6 precious metals analysis methods to maximize efficiency

Malvern Panalytical offers a full portfolio of interconnective analytical instruments for precious metals applications. The technologies we offer include X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD) spectroscopy, near-infrared (NIR) spectroscopy, laser diffraction, pulsed fast thermal neutron activation (PFTNA), and physical gas absorption.

1. X-ray fluorescence (XRF)

XRF spectroscopy is a non-destructive technique widely used for rapid compositional analysis of metals. It is especially useful for precious metals analysis because it can directly analyze concentrations of metals such as gold, silver, and platinum, whereas other methods detect the minerals surrounding these metals.

XRF achieves this analysis by directing X-rays at a sample, causing its atoms to emit secondary (fluorescent) X-rays. These emitted X-rays are characteristic of the elements present, enabling precise identification and quantification.

Advanced technologies like the X-550 handheld XRF analyzer from SciAps bring this speed, precision, and accuracy to precious metals exploration. The lightweight handheld device delivers positive material identification for most alloys in just one second, helping identify even small amounts of valuable ores.

Meanwhile, lab-based XRF spectrometers like our Epsilon 1 benchtop instrument can help you quantify the concentrations of gold, silver, platinum, palladium, and other elements in your ores. This is all in a compact format that can be placed close to the exploration site.

Finally, XRF can deliver real-time insights into your process line. The Epsilon Xflow is a high-performance XRF system that enables online analysis of leaching solutions and other process liquids, helping you optimize reagents and thereby reduce costs and environmental impact.

2. X-ray diffraction (XRD)

XRD reveals the crystalline structure and phase composition of materials. When X-ray beams interact with a crystalline substance, they produce diffraction patterns that are unique to the material’s internal structure. These patterns help identify ore types, monitor phase transitions during processing, and detect unwanted impurities.

The Aeris compact XRD system exemplifies accessible mineralogical analysis. Its compact format means it can be moved and fitted easily into any environment, including at-line or in small-scale, in-field container labs. It functions as a black-box solution, enabling even novice users to obtain measurements they can use with very little training at various stages in the precious metals mining process.

3. Near-infrared (NIR) spectroscopy

NIR spectroscopy is a non-destructive technique that uses light in the near-infrared range (around 700 to 2,500 nanometers) to characterize a material’s molecular makeup. It works by measuring and identifying the characteristic reflectance spectra produced by different chemical compounds when they are exposed to NIR light.

NIR spectroscopy’s portability, minimal sample preparation requirements, and non-destructive nature make it especially useful during precious metals exploration. It can identify minerals that are used as “tracers” for precious metals deposits, enabling mining professionals to detect less accessible ore deposits.

NIR instruments can be tailored to different stages of gold exploration and processing. Handheld instruments like the SciAps ReveNIR help geologists identify gold deposits, while Malvern Panalytical can help design on-belt solutions for processing applications.

4. Pulsed fast thermal neutron activation (PFTNA)

PFTNA offers a non-destructive method for continuous bulk elemental analysis. It works by bombarding materials with fast and thermal neutrons, prompting the emission of gamma rays from various elements. These gamma rays are then detected and analyzed to determine elemental composition.

This method is particularly useful for in-line or conveyor-belt monitoring, providing real-time data for process control. PFTNA does not measure precious metals directly. However, the insights that systems such as the CNA Pentos deliver on the mineralogical makeup of your ores offer a powerful option for ore sorting that can be further explored in collaboration with Malvern Panalytical.

5. Laser diffraction

Laser diffraction is a particle size analysis technique commonly used in precious metal processing to evaluate the distribution and fineness of crushed and milled ores. The method works by passing a laser beam through a dispersed sample of particles; the way the light scatters is measured and analyzed to determine particle size distribution.

This information is critical, as particle size has a direct impact on flotation and leaching efficiency, chemical consumption, and overall gold recovery. Smaller, uniform particles generally allow for more effective chemical interaction, while oversized or inconsistent particles can hinder processing.

In gold processing specifically, particle size and shape have a significant impact on preg-robbing. Smaller particles in carbonaceous materials have a larger surface area, increasing the likelihood of adsorbing gold from solution. Malvern Panalytical offers particle-sizing instruments for both the lab and the process line. The Mastersizer 3000+ Ultra can provide high-accuracy measurements of particle sizes in the 0.01µm – 3,500µm range for laboratory analysis, while Insitec is placed in-line to provide direct, real-time particle size data.

6. Gas adsorption analysis

Gas adsorption refers to the process whereby gas molecules adhere to the surface of solid materials. Analyzing this behavior using the Brunauer-Emmett-Teller (BET) theory gives insights into the structural analysis of material porosity.

Gas adsorption analysis with instruments like the ASAP 2020 Plus from Micromeritics can help precious metals mining professionals mitigate threats including preg-robbing.

By measuring the surface area, pore size distribution, and total pore volume of carbonaceous ores, mining professionals can identify which ores will need to be pre-treated with techniques such as roasting. This helps safeguard yield and boost profits.

Connect precious metals analysis methods to boost your yield

Each of these techniques plays a vital role in precious metals analysis. As a full portfolio provider of these solutions, Malvern Panalytical can help you achieve a complete, interconnected analytical solution to improve efficiency at every stage of the precious metals mining process.

Contact us if you’d like to find out more about Malvern Panalytical’s out-of-the-box and tailor-made solutions.

Further reads:

• 6 Precious metal analysis methods using advanced analytical technologies
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• Solving mining challenges with the new Revontium™ XRF instrument