Suppressed Knowledge in Fine Gold Recovery: A Barrier to Mercury-Free Artisanal Mining

Artisanal and small-scale gold mining (ASGM) supports millions of people worldwide, particularly in Africa, but remains heavily reliant on mercury amalgamation — a practice that causes severe health and environmental damage. Simple, low-cost gravity concentration technologies could dramatically reduce or eliminate mercury use, yet some promising approaches have faced barriers to widespread adoption and documentation.

One notable example is a 2003 comparative test program conducted byAaron James Gunson at the University of British Columbia (UBC). The unpublished 18-page internal report, titled Cleangold Test Program, evaluated the Cleangold magnetic sluice — a simple, inexpensive device using magnetic riffles to capture fine gold — against other gravity concentrators, including centrifugal units like the Knelson concentrator.

The tests reportedly showed the Cleangold sluice achieving high recovery rates (around 90% or better with re-processing) for very fine gold particles down to ~30–50 microns, performing comparably or slightly better than more complex equipment in certain fine-fraction scenarios. This suggested strong potential for artisanal miners who lack access to powered, high-maintenance machinery.

A revised and publicly available version of related work appeared inGunson’s 2004 M.A.Sc. thesis (Mercury and Artisanal and Small-Scale Gold Miners in China), which focused on broader mercury issues and alternative technologies but omitted the specific Cleangold-vs-centrifugal comparison.

Robin Grayson’s comprehensive 2007 review, Fine Gold Recovery –Alternatives to Mercury and Cyanide (World Placer Journal, Vol. 7, pp. 66–161), cites the 2003 Gunson report as evidence of the Cleangold sluice’s effectiveness for ultra-fine gold. Grayson describes the Cleangold as recovering 60–70% of gold per pass (up to ~90% with a second pass) down to 0.005 mm, positioning it as a standout low-cost mercury alternative.

Knelson Concentrators, founded in British Columbia by Byron Knelson, maintained strong ties to the Canadian mining academic community, including equipment provision, laboratory testing, and industry connections at institutions such as UBC’s Norman B. Keevil Institute of Mining Engineering. (A memorial scholarship in Byron Knelson’s name continues to support mineral processing students at accredited Canadian universities.)

The Social Cost of Suppressed Knowledge

Suppressing or limiting the dissemination of independent comparative studies on low-cost gravity technologies is socially degradable. It delays the transfer of practical, affordable solutions to the very communities most affected by mercury pollution.

Instead of prioritizing simple tools that small-scale miners in Africa can build, maintain, and afford locally, the focus often shifts toward more capital-intensive equipment. Large companies with commercial interests in selling advanced concentrators may indirectly influence research priorities or publication pathways — even when the evidence points toward equally effective, lower-barrier alternatives.

This dynamic hinders genuine technology transfer and perpetuates dependency on mercury or expensive imported machinery. As a mentor in the Start Your Own Gold Mine program, I see daily how accessible, mercury-free methods could transform lives if freely shared and taught.

References

• Gunson, A.J. (2003). Cleangold Test Program. Unpublished internal report, University of British Columbia, Vancouver, 18 pages. (Cited in Grayson 2007)

• Gunson, A.J. (2004). Mercury and artisanal and small-scale gold miners in China. M.A.Sc. thesis, University of British Columbia. Full PDF: https://open.library.ubc.ca/media/download/pdf/831/1.0081074/1

• Grayson, R.F. (2007). Fine Gold Recovery – Alternatives to Mercury and Cyanide. World Placer Journal 7: 66–161. Full PDF available via ResearchGate: https://www.researchgate.net/publication/314237371_Fine_Gold_Recovery_-_Alternatives_to_Mercury_and_Cyanide_Purpose_of_study (See reference #172 for the Gunson 2003 report; Cleangold sluice discussed as method #58)

• Additional context on Knelson–UBC ties appears in departmental lab descriptions, student resumes, and industry histories (e.g., Knelson equipment routinely used in UBC mineral processing teaching and research).

Open access to such knowledge is essential. Suppressing it does not serve the miners, the environment, or the long-term health of gold-producing communities. Let’s prioritize teaching what actually works on the ground.