ARTGoldTM: A breakthrough in detrital gold grain, down to the micron!

By IOS team, February 18, 2016

While gold grains' counting in glacial sediment is a well-established exploration technique, it is surprising to see how this technique relies upon artisanal methods such as hand panning and shaking table. The technique fundaments did not evolve in the last 40 years until  we introduced ARTGoldTM, a game changer!

Despite the fact that we operate in IOS a heavy mineral laboratory for more than 23 years, we always been reluctant to recommend gold grains counting to clients due to its poor reproducibility and lack of robustness, being too sensitive to operator skills and moods to be used other than for preliminary prospecting work. Therefore, we traditionally recommended to our clients to use a procedure based on the chemical assay of parameterized Falcon or Knelson centrifuges, far more reproducible. However, in the last three years, IOS conducted an extensive research program in order to develop a robust gold grains counting protocol insensitive to the human factors. No more panning!

ARTGoldTM (Advanced Recovery Technique) consists of a chain of innovations acting on the complete sample processing cycle: concentration, counting and characterization of microns scale gold or PGM grains. The first cornerstone is a proprietary gold grain concentration device, built like a fluidized bed. This device enables a recovery in excess of 90% on grains down to 5 microns and replaces the conventional shaking table, goldhound spirals, centrifuge or "pans" as used by competition. It produces a super-concentrate, about 300 milligrams, representing a concentration factor of 30,000 to 50,000x, the efficiency of which being basically not dependent on the operator's skills. Furthermore, the device can be used as an apron feeder on a shaking table for the production of conventional heavy minerals preconcentrates.


ARTGoldTM Fluidized bed for gold grains recovery

The super-concentrate is sieved at 50 microns, and the > 50 µm is check optically, while the < 50 µm is sent to an electronic microscope. The optical check is done under an apochromatic stereomicroscope at a magnification up to 106x. Grains are extracted, photographed and identification certified under the electronic microscope.

The fine fraction (< 50 µm) is dusted on a custom holder and check under a Zeiss EVO MA15-HD electron microscope with a backscattered electrons detector. The thoroughly automated routine, based on Oxford Instruments' Aztec platform, scan a mosaic of the holder surface in search of heavy minerals, acquire an EDS-SDD spectrum on detected grains and classify the minerals. Finally, it acquires a high magnification image on the gold and PGM grains for shape classification and measurements, presented in a certificate.


SEM-based automated gold and PGM grains detection

Efficiency of the method is stunning! The grain count is multiplied by 10x compared to conventional methods, efficiency of which collapses below 50 microns. The grain size distribution curve is maximal at 20 microns, similar to what is observed by ore petrography. This enables to reduce the detection limits of the method below background values, thus enabling to establish a proper anomaly threshold, or to simply work with smaller sample size. Economy at sampling is self-evident, especially for programs conducted in remote areas or by drilling. Furthermore, specific details of grain morphology are observable and indicate that small grains are less modified through displacement in sediments. Thus, their morphology relates more to their relation with host minerals at the source. Insights on deposit types are gained, backed by the EDS-SDD chemical analysis. The classical "pristine", "modified" and "reshaped" classification is to be redefined.

The ARTGoldTM technique enables the simultaneous recovery and counting of any minerals denser than about 5 g/cc. A grain analysis is concomitantly obtained for minerals such as scheelite, wolframite, cassiterite, columbotantalite, uranothorite, galena, monazite, barite, cinnabar etc. The technique is astonishingly efficient at recovery of platinum group minerals, which are typically smaller than 20 microns, such as sperrylite, merenskyite, isoferropalladium, PGM alloys, etc. Although the exact proficiency still has to be measured accurately, the technique seems to outperform any other methods available for the exploration of these precious commodities.

ARTGoldTM will be a game changer in this segment of the industry!



  1. BSD mosaic with grain classification in color. As reference, the quartz grain at the top is 1 mm across.
  2. High magnification image of a crystalline gold grain from a till sample, Wawa area, Ontario.
  3. High magnification image of a sperrylite grain (PtAs2), Sudbury, Ontario.
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