Project EG/GLO/01/G34 Removal of Barriers to Introduction of Cleaner Artisanal Gold Mining and Extraction Technologies Manual for Training Artisanal and Small-Scale Gold Miners Global Mercury Project, Coordination Unit, Vienna Pablo Huidobro, Project Manager, UNIDO Marcello M. Veiga, Chief Technical Advisor, UNIDO Svitlana Adler, Administrative Assistant, UNIDO Authors (UNIDO Consultants) Marcello M. Veiga1, Stephen M. Metcalf1, Randy F. Baker2, Bern Klein1, Gillian Davis1, Andrew Bamber1, Shefa Siegel1, Patience Singo3 1 University of British Columbia, Norman B. Keevil Institute of Mining Engineering, Vancouver, BC, Canada 2 Azimuth Consulting Group, Vancouver, BC, Canada 3 Good Life Investments, Bulawayo, Zimbabwe Editing: Marcello Veiga, Stephen Metcalf and Karel Young Covers: Front: Training Miners in Mozambique, Back: Training in Indonesia, Brazil, Sudan, Laos, Tanzania and Zimbabwe Disclaimer: The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever of the Secretariat of the United Nations Industrial Development Organization (UNIDO) concerning the legal status of any country, territory, city or area of its authorities, or concerning the delimitation of its frontiers or boundaries. Mention of company names and commercial products does not imply the endorsement of UNIDO. Copyright UNIDO, 2006 Manual for Training Artisanal and Small-Scale Gold Miners _________________________________ Copies can be obtained at: Global Mercury Project UNIDO, Vienna International Center, D-12 P.O. Box 300 A-1400 Vienna, Austria www.globalmercury.org/ _________________________________ Less mercury, more gold and better health (Gold in a shop in Kalimantan, Indonesia) Manual for Training Artisanal and Small-Scale Gold Miners/Veiga, M.M. et al./Vienna, Austria: GEF/UNDP/UNIDO, 2006, 144p. 1. mercury pollution, 2. artisanal gold mining, 3. gold processing. GMP - Manual for Training Artisanal and Small-Scale Gold Miners i Table of Content Introduction to Effective Training Strategies ............................................ 1 Who are successful trainers? ................................................................ 1 What is a successful curriculum? ......................................................... 3 How do we recognize successful implementation? .............................. 6 Basic knowledge for trainers ................................................................ 6 Gold Ores, Mineralogy and Liberation ..................................................... 7 Gold occurrence.................................................................................... 7 Gold minerals ....................................................................................... 8 How to find gold deposits..................................................................... 9 Gold liberation.................................................................................... 10 Using a small ball mill to investigate gold liberation ......................... 12 Basic knowledge for miners ............................................................... 14 Crushing and Grinding............................................................................ 16 Why crushing and grinding is important ............................................ 16 Crushing ............................................................................................. 18 Grinding.............................................................................................. 25 Basic knowledge for miners ............................................................... 32 Gravity Concentration............................................................................. 34 Introduction ........................................................................................ 34 Sluices ................................................................................................ 37 Good sluice design ............................................................................. 38 Feed preparation ................................................................................. 41 Sluice design and construction ........................................................... 42 Trapping mechanisms......................................................................... 43 Optimal slurry flow velocity............................................................... 46 Centrifugal concentrators ................................................................... 47 Panning............................................................................................... 49 Different kinds of gold pans ............................................................... 50 Basic knowledge for miners ............................................................... 53 Gold Amalgamation ................................................................................ 55 Mercury, a brief history...................................................................... 55 Mercury uses and properties............................................................... 56 Forming gold amalgam....................................................................... 57 Improving amalgamation.................................................................... 61 Amalgam-heavy minerals separation ................................................. 63 Separating excess mercury from amalgam ......................................... 64 Hotspots.............................................................................................. 66 Mercury recovery by retorting............................................................ 67 Classical retorts .................................................................................. 70 ii GMP - Manual for Training Artisanal and Small-Scale Gold Miners Operating retorts .................................................................................72 Home-made retorts..............................................................................73 How to reduce the retorting time ........................................................81 Recycling mercury..............................................................................83 Melting gold........................................................................................84 The Ratio of Mercury Lost to Gold Produced (Hglost:Auproduced).........85 Amalgamation centers ........................................................................86 Effects of mercury vapor exposure .....................................................87 Basic knowledge for miners................................................................89 Cyanide Leaching of Gold.......................................................................92 Introduction.........................................................................................92 Toxicity of cyanide .............................................................................93 Cyanide leaching.................................................................................95 Interferences to cyanide leaching........................................................96 Industrial practices..............................................................................97 Recovering gold from the pregnant solution.....................................102 Cyanide management........................................................................106 Basic knowledge for miners..............................................................108 Environmental Effects of Mercury ........................................................110 How mercury contaminates the environment....................................110 Protect your environment..................................................................111 Basic knowledge for miners..............................................................112 Health Consequences of Mercury Exposure..........................................115 Mercury in the environment..............................................................115 Human exposure to mercury.............................................................116 Uptake and elimination of mercury ..................................................118 Medical indicators of mercury exposure...........................................119 Symptoms of mercury vapor exposure .............................................120 Consequences of mercury exposure..................................................121 Treatment of mercury poisoning.......................................................123 Protect yourself and your family.......................................................123 Basic knowledge for miners..............................................................124 General Health Concerns of Artisanal Mining Communities ................126 Malaria..............................................................................................127 Tuberculosis (“TB,” “consumption”)................................................128 HIV/AIDS.........................................................................................128 Malnutrition ......................................................................................129 Conclusion ........................................................................................130 Basic knowledge for miners..............................................................130 Clean Water and Sanitation ...................................................................132 Why clean