Portable XRF for Gold (Au) and Au Pathfinders for Mineral Exploration and Ore Body Vectoring
by Philippine Resources - December 07, 2021
Olympus’ X-ray fluorescence (XRF) analyzers provide high-performance, real-time geochemical data for rapid multielement characterization of soil, rocks, and ores.
Recent advances in XRF technology have increased the number of elements measured, improved the limits of detection, and reduced analysis test times.
Vanta™ XRF analyzers provide convenient and rapid measurement of many types of samples associated with Au exploration, within Au mines, Au mine labs, and refined Au products.
- Rapid indication of potential Au mineralization through XRF analysis of pathfinder elements in soil, drill cuttings, and drill cores
- Priority sample selection, maximization of analytical budgets, and improved drill target generation by prescreening samples with XRF
- Improved ore deposit understanding, modelling, and vectoring with less dilution and better Au recovery via XRF mapping of structural features and identification of mineralized and altered zones
- Inexpensive and rapid rock typing by using XRF for lithogeochemistry
Pathfinder and Alteration Geochemistry
Most Au deposits have an associated geochemical signature (as shown in the table above). The XRF analyzer can detect these geochemical signatures, enabling geologists to better understand the geological system in which they are working. Typical Au pathfinder elements include As, Cu, Pb, Zn, Sb, Bi, Ag, and W.
Typical XRF LODs for Common Au Pathfinder Elements with Vanta VMR GeoChem Model
XRF Analyzer for the Detection of Gold
It is common knowledge that handheld XRF analyzers do not support direct low level measurement of Au in geological samples (e.g., low ppm and ppb). The lab-based fire assay technique is commonly recognized as the method of choice for Au analysis. Au L-level X-ray lines are located in a very crowded area of the X-ray fluorescence energy spectrum. In this part of the spectrum, interference from other elements (e.g., As, Zn, W, and Se) can yield a false-positive Au determination.
Direct measurement of Au by XRF can be achieved in specific cases such as high-grade (> 5 ppm) quartz vein environments (relatively interference free) or within refined Au products (where Au is present in very high concentrations).
An increasing number of Au onsite mining laboratories are using XRF in place of, and as a supplement to, fire assays methods. Please refer to the Olympus Application Note “Use of Handheld XRF in Au Mine Laboratories.” Mines are also using Olympus handheld XRF analyzers for measuring Au in activated carbon. Please refer to the Olympus application note, "Measuring Gold in Activated Carbon."
Philippine Resources - August 31, 2021
Automated, Robotic Innovations for Analyzing Geological Samples with Portable XRF
By Todd Houlahan Advances in robotics are leading to faster and more efficient X-ray fluorescence (XRF) analyses for geo-exploration projects. One new robotics innovation revolutionizing XRF analysis is GERDA, the automated Geochemical Research and Documentation Assistant. Created by the MEFFA Lab Oy in Finland, the automated unit is designed to test core in core boxes and soil, sediment, and crushed rock in plastics bags to achieve higher sample throughput with your portable XRF analyzer. The system is set up on a CNC table with a Vanta™ handheld XRF analyzer, a high-resolution USB camera, a simple control module based on Raspberry Pi 3, and easy-to-use software for visualization of results and data processing. In parallel with GERDA, the inventors have started to develop a unique method known as Nugget Effect Gold Assay (NEFFA) to estimate gold mineralization in samples (typically crushed rock or crushed drill core). Read on to learn more! GERDA is used with a Vanta XRF analyzer to automate testing for geoexploration projects. Developing the GERDA System The GERDA system was developed by a team that has been using portable XRF analyzers on mineral exploration projects for over 15 years. Largely focused on the use of pathfinder elements as part of their gold exploration projects, the inventors have witnessed the development of portable XRF analyzers over time, particularly the improvements in speed and the reduction in the test times required to achieve the levels of precision needed. They have also observed Olympus’ developments in detector technology and signal processing and, in particular, the Vanta analyzer’s ability to achieve lower limits of detection (LODs) of elements, including gold (Au). As junior explorers on a limited budget, their focus has been on greenfield exploration, rapid identification of anomalies, generation of drill targets, and potential new discoveries, not resource definition. Key to this has been their ability to test a far greater number of samples using their portable XRF analyzers than would be possible if all samples were assayed in the lab. GERDA is critical to their ability to do this. GERDA is designed to: Increase sample throughput for existing portable XRF owners Help select samples for more expensive laboratory assay Provide faster access to meaningful results for real-time follow up/infill Reduce the overall cost of exploration analytical budgets Make exploration programs more efficient To see how GERDA works with portable XRF, watch this quick video: https://www.youtube.com/watch?v=3-Gesp0Gjpk What is Nugget Effect Gold Assay (NEFFA)? To understand this new technique, it is important to know how the “nugget effect” works. The nugget effect is a term used to describe the sampling problem that can occur when there are large gold particles (nuggets) in a sample. If a nugget is selected during a traditional sampling process, researchers can overestimate the amount of gold in the sample. But if the nugget is missed, the gold can be underestimated. For gold exploration and mining, this variability can lead to inaccurate results and costly mistakes. The Nugget Effect Gold Assay (NEFFA) technique aims to turn the traditional challenge associated with the nugget effect into an opportunity. NEFFA attempts to measure the nugget effect through multiple nondestructive, systematic analyses of a geological material (typically crushed rock or crushed drill core) to identify the presence of gold or other precious metals based upon its distribution within the sample. NEFFA completely redefines and reduces the traditional sample preparation procedure and aims to provide semi-quantitative gold results using portable XRF analyzers to identify samples of potential interest for further laboratory analysis. Here’s how it works: Representative samples of 20–30 g, depending on the nature of material, are isolated in a medium such as a clear sample bag or under plastic film to ensure that there’s no contamination from an external agent The sample is distributed evenly over a 10 cm × 10 cm square with the depth of the material being no thicker than 2 mm A grid or matrix is placed over the sample, with individual matrices measuring 1 cm × 1 cm Measurements are performed within each square cm, and the average of all results is reported The technique is most effective on crushed rock or crushed drill core samples with a grain size 3 mm, but not on homogenized pulp samples Rotary air blast and reverse circulation (RC) samples can be analyzed directly This method takes the throughput advantages of GERDA for general exploration projects and adds additional value for gold exploration by providing gold estimates using XRF. We acknowledge this method may be considered non-traditional. Portable XRF’s weaknesses in analyzing gold are well known (elemental spectral overlaps can cause false positives, relatively high LODs compared to the lab, and fire assay is the best technique to use), however the inventors’ initial work using GERDA and NEFFA suggests meaningful gold data and cost savings are possible with this system. Also, local radiation safety and licensing requirements must be followed with any proposed implementation of this technique. By Todd Houlahan - Director, International Mining Group Todd graduated from the University of Newcastle, Australia in 1993 with a degree in soils and hydrology. For the past 18 years, Todd has been a leader in the portable XRF revolution in the mineral exploration and mining industries, publishing numerous papers on the subject and presenting at international conferences. For the past 10 years, Todd has led Olympus’ International Mining Group helping explorers, miners, and their shareholders achieve cost efficiencies by using the best portable XRF and XRD technology solutions. To know more about Automated, Robotic Innovations for Analyzing Geological Samples with Portable XRF, visit https://trisco.com.ph/ or email at email@example.com
Marcelle P. Villegas - January 22, 2022
Senator De Lima passed a resolution against lifting of open-pit mining ban
Before the year ended, DENR Secretary Roy Cimatu signed the Department Administrative Order (DAO) No. 2021-40 that lifts the ban on open-pit mining. The order was passed last 23rd of December 2021. This covers mining for copper, gold, silver and other complex ores. DENR made this decision with hopes to revive the mining industry so it may once again provide job opportunities in rural areas. This decision was a response to counter the economic downturn that resulted from the global pandemic.
Philippine Resources - January 21, 2022
WIDENING OF LAWTON AVENUE IN TAGUIG CITY FINISHED BY Q2 OF 2022
Photo credit: Department of Public Works and Highways The Department of Public Works and Highways (DPWH) has fast-tracked the widening works at Fort Bonifacio-Nichols Field Road or Lawton Avenue in Taguig City to meet its target completion by the second quarter of 2022. “As the government increases mobility in Metro Manila amid the pandemic, this project is vital in addressing traffic woes experienced by motorists,” said DPWH Secretary Roger G. Mercado during project inspection on Thursday, January 20, 2022, along with Senior Undersecretary Rafael C. Yabut, Assistant Secretary Wilfredo S. Mallari and National Capital Region (NCR) Director Nomer Abel P. Canlas. The road widening has three phases with the 1.34-meter Phase 1 traversing from 5th Avenue to Bayani Road completed and opened to the public on November 17, 2020. “We are keen in expediting the completion of the remaining two phases of the project with Phase 2 covering 1,100 lineal meters from Bayani Road to Philippine Navy and Phase 3 covering 240 lineal meters from Philippine Navy to Pasong Tamo Extension,” said Secretary Mercado. Once fully completed, the 3.1-kilometer, four (4)-lane Lawton Avenue will be converted into a six (6)-lane thoroughfare that can accommodate influx of vehicles traversing the area and will help decongest traffic in nearby Epifanio delos Santos Avenue (EDSA), South Superhighway and C-5 Road. It will also complement the 961.427-lineal meter Bonifacio Global City-Ortigas Center Link Road Project which has improved access to and from the cities of Taguig, Pasig, Makati and Mandaluyong. The widening of the Lawton Avenue is part of the EDSA Decongestion Program, one of the flagship projects of the Duterte administration under the Build Build Build Program.
Philippine Resources - January 19, 2022
Vulco® R67 mill lining rubber compound is revolutionising mine site mill operations
Photo: Inside the discharge end of a ball mill being fitted with spiral lifters and rubber grates. Vulco® R67 mill liners last significantly longer and deliver a measurable reduction in mill downtime, installation and maintenance costs. Vulco® rubber is renowned throughout the mining industry for its exceptional wear life and reliability in mill lining systems. These abrasion- and impact-resistant rubber compounds have been developed with advanced technologies by the Weir Minerals’ team of expert engineers and material scientists who are continually refining Vulco® rubber products to keep them at the forefront of mill lining systems technology. Having identified a need for higher-wearing rubbers for mill lining systems, the material science experts commenced developing an industry leading, premium-grade rubber compound with superior wear life and performance in mill lining applications. The result was the Vulco® R67 rubber – an optimum material which is manufactured with proprietary new compounds and innovative methods of processing to deliver outstanding wear life and longer uptime. Extensive field research, compound testing and site trials were conducted to ensure that it was not only able to withstand severe abrasion in typical mill system applications, but that it is best in class. In fact, it has been the most wear-resistant rubber compound that Weir Minerals has ever developed for mill lining applications. The R67 compound boasts a high hardness, elongation, tensile and tear strength, and is suitable for lifter bars, head/shell plates and grates. When it’s utilised in conjunction with metal cap mill liners, the result is a versatile, economical and efficient product that weighs up to 50% less than steel alone. The added benefit is a lighter product that’s faster, easier and safer to install. Revolutionising wear lining Since its launch in 2018, many mining operators from around the globe have implemented the R67 compound into their mill lining systems. They have reported as much as 20-40% improvement in wear life, which is resulting in fewer mill lining replacements and longer mill campaigns. This reduction in shutdowns has a dual benefit of increased cost savings and improved plant availability. What are the benefits for the mill operators? With a liner that can run significantly longer, operators have experienced a wide range of benefits including: Improved wear life A measurable reduction in mill downtime Increased uptime and processing Easier and safer installations Reduced maintenance costs In addition to this, the mines benefit from having an experienced and dedicated team from Weir Minerals who custom-engineer the liners to suit each mill’s unique requirements for optimal wear life. Global in-field success The R67 elastomer compound is changing the way mills operate - with exceptional results. Extensive global trials and commercial installations in the market have resulted in a number of successful outcomes across a variety of different grinding applications. From mines in the USA to Chile, the R67 has proven its outstanding performance consistently. As an example, a high-grade nickel and copper mining project in the USA had a problem where the liners in one ball mill were wearing out too quickly, leading to continued downtime and reduced processing. They were looking for a product significantly superior to the elastomer that they were using. Initially there was reluctance from the mine, as they had loyalty to their original mill supplier, however after Weir Minerals conducted a series of trajectory simulations and discreet modelling - to optimise the design and deliver the best process performance for the mill, they agreed to trial the R67 liners. At the end of the trial the R67 showed 30-40% better performance than the incumbent liners and the customer installed a full set of R67 liners in their mill. Another trial in the USA took place in an iron ore mine with several dozen ball mills in operation. Here, Vulco® R67 liners delivered a 17% increase in life compared to the failed shell plates from the mine’s original mill lining system supplier. The company was extremely impressed with the results and installed a complete shell liner in their ball mill. Moving to Chile, a copper mine was keen to trial the R67 compound to see if they could improve the wear time of a competitor rubber liner. After a three-month trial, all liners were physically measured showing that the Vulco® R67 liners fully worn wear life projected from the actual wear would be 80% longer compared to the incumbent liners. Another copper processing plant in Chile trialled R67 composite liners in their SAG mill against two other compounds that are commonly used in the industry. After 12 months, there was a 48% and 62% wear life improvement on the other liners – proving that the R67 composite liners could withstand the highly abrasive environment. Helping customers optimise their process As leaders in material technology, Weir Minerals are continuously undertaking research and development to provide best-in-class products to mining customers, while helping them improve their bottom line. When using Vulco® R67 rubber compounds, our customers can feel assured they have a market-leading product that is backed by decades of experience, expertise, and proven effectiveness. This innovative rubber compound not only delivers superior physical and viscoelastic properties but is also a lighter and safer material to use. Where can you find Vulco® R67? Vulco R67® mill liners are made exclusively at Weir Minerals facilities in North and South America, Australia and South Africa, with plans to expand production into more regions in the future.