Just a decade ago, a handheld point-and-shoot x-ray fluorescence (XRF) instrument was considered a cool but rare toy to play with in the field on a remote greenfield exploration project. If held in place long enough, it would detect a small range of chemical elements in a handful of soil. Fast-forward ten years and the cool toy has evolved into an industry staple, with a variety of instruments and uses across the entire mining value chain.

Portable XRF (pXRF) tools have been joined by other miniaturized laboratory technologies, including portable x-ray diffraction (XRD) and laser induced breakdown spectroscopy (LIBS) to name a few. Just like their laboratory-based cousins, these scientific instruments bounce an x-ray or laser beam off the atoms or crystals within a rock, soil or core sample to identify the elements and minerals it contains. Now able to detect a wider range of elements more precisely and identify elements and minerals in only a few seconds, these instruments are generating quality data in real-time to help make informed decisions in the field and on the mine site.

A new sector of specialists has grown around the use of these instruments and the treatment of the data they generate, and several global companies such as Olympus Scientific Solutions, Thermo Fisher Scientific, Bureau Veritas and many smaller ones are racing to push these technologies to the limits. Ensuring the quality of the data collected, integrating the volumes of data generated by these tools with other geoscience data, and sharing the information securely through the cloud for real-time decision-making are priorities for the sector. New instruments and software packages are hitting the market every few months.

Filling out the periodic table

“Originally, portable XRF started as a straightforward exploration tool for regional soil surveys,” said Aaron Baensch, principal geologist of the international mining group at Olympus Scientific Solutions Americas (Analytical Instruments Division). “Ten years ago, the technology didn’t have the sensitivity to get down to single parts-per-million for a lot of elements, and it struggled with the light elements, like potassium and calcium, that we use for mapping alteration in mineral systems.”

At first, the lightest element by atomic weight on the periodic table that pXRF could accurately detect was titanium, number 22 on the periodic table. Now, all the major rock-forming light elements, including aluminum, silica, phosphorus, sulfur, potassium, calcium and magnesium, can be detected down to single parts-per-million (ppm). These elements are the majority constituents of most rocks and so are critical for their identification.

“These instruments have come down two orders of magnitude in sensitivity on the major transition elements,” said Baensch. “Copper, for example, was at 100 ppm a decade ago. Then, a few years ago, we got it to 10 ppm, and now it’s at one ppm.”

One of the latest tools to hit the market is the Vanta Handheld XRF Analyzer, developed by Olympus. In addition to being able to analyze a sample faster than Olympus’ previous models and being more sensitive to a wider range of elements, said Baensch, it is built for “nasty environments” like the Pilbara desert in outback Australia or the frozen tundra north of Yellowknife. It is engineered to withstand a temperature range of -10 C to 50 C (with optional fan) and passes a military-standard drop test.

“We can find almost every deposit style, from epithermal gold right through to iron ore and bauxite, with these tools,” said Baensch. “We’re working across every commodity group, and now pXRF can be used across the whole value chain.”

But pXRF, the mainstay of handheld field technology for many years, now has some healthy competition. SciAps Inc., a Boston-based instrumentation company specializing in portable analytical instruments, introduced the world’s first handheld (HH) LIBS spectrometer in 2014 and released a new model in its LIBS Spectra Z-Series in 2016. The Z-300 HH LIBS can quantify elements that a pXRF cannot measure, such as lithium, beryllium, boron, carbon and sodium, and can zoom in for a smaller spot analysis to map the distribution of elements within a single mineral grain.

The SciAps Z300 LIBS spectrometer in action at the face in an underground mine. Courtesy of SciAps

Andrew Somers, managing director of SciAps Australia and global business director for geochemistry at SciAps Inc., explained that the LIBS is “quite a different creature” and not simply the next generation of XRF. He noted that “in addition to the lighter elemental suite possible with LIBS a key point of difference is the LIBS is spatially discrete by comparison to the portable XRF. We use a 50 micron laser spot in combination with the ability to raster using an internal X-Y stage to collect analytical data.”

As always, it comes down to choosing the right tool for the job. With its much smaller spot analysis diameter, a LIBS may be the right choice if a geologist wanted to look in detail at the contact between two minerals, zones of different chemical composition within a mineral or alteration around a small vein, said Somers. However, when looking at broad chemical alteration variations associated with mineralization, the larger sample size of a pXRF may be more useful. SciAps also offers pXRF and portable Raman systems.

Geologists are increasingly spoiled for choice when it comes to handheld analysis and the range of tools available, but there are certainly challenges.

Watch SciAps CEO Don Sackett detail the latest in handheld tech for elemental analysis in the field.

 Pros and cons

“When a geologist takes a field-portable instrument in their hand, they become a laboratory,” said Britt Bluemel, geochemist at REFLEX, the Canadian distribution partner for Innov-X Technologies Canada, distributor for the Olympus range of portable tools. “Laboratories have certain responsibilities and are required to follow intense QA/QC protocols and quality checks. Individuals don’t often do this.”

Human error can be introduced at multiple places along the chain of custody, or paper trail, for each sample analyzed, said Bluemel, such as typing information into a spreadsheet or transferring between files. To minimize data handling, REFLEX has designed software to control the XRF instrument, decreasing the likelihood of human error during data collection.

“We’ve built in calibration settings to help the geologist be more like a laboratory,” said Bluemel. “For example, we can set up a custom QA/QC routine where the handheld analyzer will prompt the geologist to scan a blank every ten samples.”

Despite initial concerns, bricks and mortar commercial laboratories are still in business, even with the growth of handheld analysis technologies. Surprisingly, these instruments have created more work for laboratories, said Baensch. Now, only the “juiciest samples” are sent to the commercial laboratories for analysis.

“The labs were scared it was going to be disruptive to their business and take market share away, but what actually happened is the opposite,” said Baensch. “What we see now are customers using handheld and on-site instruments in the field to pre-screen samples and send the better samples back to the lab.”

This may be one of the biggest attractions for explorers and underground miners using these technologies: the ability to quickly have enough information available to make key decisions. If only the most promising samples are sent to the laboratory, they are analyzed quicker, and the information can be used to decide where to drill, how deep to drill, or even to stop drilling, saving time, money and resources in the field.

What’s next?

With the ability to collect more data in less time during a field program, reliable, large-scale and secure data management becomes essential. Processing, integrating, mapping and visualizing anomalies in real time requires reliable communication between the sensor, a processor and a model. Companies are using cell phones and built-in wireless technologies to transfer information from the instrument to cloud-based storage systems, such as REFLEX’s HUB. The goal, said Bluemel, is to get the data to the geological model with as little human intervention as possible.

But when field programs are remote, internet communications may be slow or unreliable, so solutions for secure camp-based quality control, storage and analytic capabilities also need to be developed. As with all internet traffic, security of the data is essential, especially with accurate metal assay numbers being collected on site and transmitted to a city-based office. Such data may be considered unpublished price-sensitive data, the custody of which must be carefully guarded and tracked to fulfill a company’s duties to the public market. New data management issues must be considered before these handhelds are used to blast every piece of rock on site, and this will likely be an area of ongoing research and development.

Once the data is captured and stored, it is not surprising that practitioners are turning to artificial intelligence and machine learning to add value. Automated analytics have a key role to play in helping to convert the huge volumes of data collected by handheld analyzers into knowledge, in real time.

“One of the biggest issues is data integration. How do you cross-correlate all of those data sets? There seems to be a lot of potential for machine learning,” said Somers. “Real time is only as fast as you can manage the data and pull it together.”

Field technologies have improved quickly and dramatically over the last decade and have certainly disrupted the way decisions are made in remote locations. Hurdles remain, but the sector is strong, competitive and focused.