Gravity Borax Method GBM Mercury Free Gold Recovery

The Gravity-Borax Method GBM is still unknown to most Artisanal and small-scale gold miners (ASGMs) worldwide as most still use mercury to extract gold. “Whole-ore amalgamation” is a technique that requires the use of 10–25 g of mercury to produce 1 g of gold. Within the last eight years, it has become evident that this technique is more widely used than earlier anticipated, and artisanal small-scale gold mining (ASGM) is now considered the single largest contributor to global mercury pollution with the environmental release of 2,000,000 lbs of mercury per year. The United Nations Environment Programme has estimated that ASGM contributes a 37% share of the anthropogenic emission of mercury to the atmosphere.

Whole-ore amalgamation is commonly practiced in the Philippines. The ore is mixed with water and crushed in a rod mill (a rotating drum with metal rods inside), after which mercury is added and milled with the ore. The gold dissolves in the mercury and forms amalgam. After the milling, the content is poured into a tub where the mercury (holding the gold) sinks to the bottom. Excess mercury is recovered, and by blowtorching the remaining bit of amalgam, the mercury evaporates leaving behind the gold.

Leach Gold Without Cyanide

In Benguet province, a group of miners have been using the mercury-free gravity-borax method (GBM) for gold extraction for decades. This method basically requires the same equipment as the amalgamation methods. However, after the rod milling, an ore concentrate holding the heavy minerals is produced by using a launder (gold sluice) and a gold washing pan. The heavy mineral concentrate is mixed with borax powder. By blowtorching the mix, the borax melts and the gold sinks to the bottom. It has recently been demonstrated that under identical conditions, GBM yields more gold than the traditional amalgamation method. Despite this advantage, GBM is not widely used outside Benguet. No earlier studies have documented that GBM can be implemented in an area using whole-ore amalgamation. Earlier technology transfer projects have promoted retorting of amalgam as a preventive technology in ASGM.

A project area in Mindanao, 20% of the miners have already converted to the mercury-free method.

Borax Method of Gold Extraction

Unfortunately, this method is ineffective in areas using whole-ore amalgamation, since up to 90% of the mercury is lost to the tailings (the waste product consisting of fine sand) and only 10% is lost by blowtorching of amalgam. Thus, only a small fraction of the mercury spill from whole-ore amalgamation can be recovered with a retort. Introduction of cyanidation techniques has also been suggested as a way to reduce or eliminate the use of mercury in ASGM. Although most cyanide compounds decompose into nontoxic forms, cyanide itself is highly toxic and exchanging one toxic chemical with another may be regarded as a controversial solution.

BORAX RECOVERS MORE GOLD than MERCURY

We present the results of a project in which GBM was introduced in two mining communities in the Philippines where whole-ore amalgamation was widely practiced. The main objective of the project was to reduce mercury pollution from small-scale gold mining by encouraging ASGMs to use a mercury free method.

Watch and Learn all about BORAX MINING USA Further References: United Nations Industrial Development Organization (UNIDO). Protocols for Environmental and Health Assessment of Mercury Released by Artisanal and Small-Scale Gold Miners. 2004. (ISBN 92-1-106429-5). 2004. http://iwlearn.net/iw-projects/1223/reports/protocols-for-environmental-and-health-assessment-of-mercury-released-by-artisanal-and-small-scale-gold-miners/view Perez E, Appel PWU, Køster-Rasmussen R. Training of Small Scale Miners and their Families in Safe Handling of Mercury During Extraction of Gold in the Philippines. Improving Access to Social Services: health services and income opportunities for Small Scale Miners and Their Families. Report for the World Bank from the Geological Survey of Denmark and Greenland (GEUS). 2007. http://www.geus.dk/program-areas/common/geus_rep_2007-35.pdf The United Nations Environment Programme (UNEP). Technical Background Report for the Global Mercury Assessment 2013. http://www.amap.no/documents/doc/technical-background-report-for-the-global-mercury-assessment-2013/848 Appel PWU and Na-Oy L. The Borax Method of Gold Extraction for Small-Scale Miners. Blacksmith Institute Journal of Health & Pollution. 2012. 2(3):5-10. http://www.journalhealthpollution.org/doi/pdf/10.5696/2156-9614-2.3.5 Ministry of Foreign Affairs of Denmark (DANIDA). Policy for Danish Support to Civil Society. 2014.http://um.dk/en/~/media/UM/Danish-site/Documents/Danida/Samarbejde/Civil-org/Dokumenter/Strat/Civilsamfundspolitik_UK_web.pdf Ministry of Foreign Affairs of Denmark (DANIDA). The Right to a better life – Strategy for Denmark’s Development Cooperation. 2012. http://um.dk/en/~/media/UM/English-site/Documents/Danida/Goals/Strategy/13287_DANIDA_strategiformidling_UK_web.pdf Rogers EM. Diffusion of innovations. Fifth edition. Free Press. 2003. Heinemann Media, Diálogos, and LO/FTF Council.

Kristensen AKB, Thomsen JF, and Mikkelsen S. A review of mercury exposure among artisanal small-scale gold miners in developing countries. Int Arch Occup Environ Health. 2013; DOI 10.1007/s00420-013-0902-9

Smallwood CL, Lipscomb J, Swartout , et al. Toxicological review of boron and compounds. Washington, DC. U.S. Environmental Protection Agency. 2004:1-88.

European Food Safety Authority Panel on Food Additives and Nutrient Sources added to Food. Scientific opinion on the re-evaluation of boric acid (E 284) and sodium tetraborate (borax) (E 285) as food additives. EFSA Journal. 2013;11(10):3407.

European Chemicals Agency. [accessed March 2015] EU candidate list of substances of very high concern. http://echa.europa.eu/candidate-list-table

Scialli AR, Bonde JP Brüske-Hohlfeld I, Culver BD, Li Y, and Sullivan FM. An overview of male reproductive studies of boron with an emphasis on studies of highly exposed Chinese workers. Reproductive Toxicology. 2010;29:10-24

http://www.journalhealthpollution.org/doi/pdf/10.5696/2156-9614-2.3.5

[accessed March 2015] Rather rich and healthy than poor and poisoned – Gold extraction with borax for small scale miners. 2012. http://www.youtube.com/watch?v=X6Sawj0HyF0

Alternative to Mercury GOLD MINING EQUIPMENT without Hg

Click these mercury-free gold extraction machines images to learn more.



Also see UNEP.