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Case Study

Testing Local Conditions for the Introduction of a Mercury-free Extraction Method using Borax in Zimbabwe

Nadine Steckling1*; Stephan Bose- Background. Mercury is extensively used in artisanal small-scale in many parts of the O’Reilly1,2; Dennis Shoko3; Stefan world, including Zimbabwe. Mercury-free mining technologies are urgently needed to protect the Muschack4; Rudolf Schierl1 biophysical environment and human health. Objective. The testing of local conditions for the introduction of a mercury-free gold mining technology entailing the use of borax in a field project in Kadoma/Zimbabwe. 1 University Hospital Munich, Institute Materials and Methods. A one-day theoretical workshop and a two-day practical demonstration and Outpatient Clinic for Occupational, were conducted in Kadoma/Zimbabwe in December 2013. The willingness of the miners to Social and Environmental Medicine, WHO change to another gold extraction technology other than mercury amalgamation, the local Collaborating Centre for Occupational availability of appropriate materials and equipment, and the suitability of the for applying the Health, Ziemssenstr. 1, D-80336 borax technology for gold were used as variables to test local conditions for introducing Munich, Germany the borax method. Simple methods like trial and error and the collection of indices during 2 UMIT–University for Health Sciences, discussions and observations were applied. Medical Informatics and Technology, Results. 1.11 grams of gold from half a ton of ore was the result of the demonstration. A number Eduard Wallnoefer Center 1, of potential improvements to the process were identified. A total of 50 invited local stakeholders A-6060 Hall i.T., Austria took part in the theoretical workshop, and 30 to 40 decided immediately to also participate 3 Tailjet Consultancy Services, 4 Tor Road, in field demonstrations. The project team noticed that the local miners were interested and Vainona, Borrowdale, Harare, Zimbabwe impressed by catching very fine gold particles with the borax method. 4 Bielefeld University of Applied Sciences, Conclusions. The project confirmed that the local conditions in Kadoma are appropriate for

Kurt-Schumacher-Straße 6, D-33615 mining mercury-free gold. The optimization and comprehensive introduction of the borax Bielefeld, Germany method in the Kadoma gold mining region is recommended to eliminate the use of mercury. Competing Interests. The authors declare no competing financial interests. Corresponding Author: Keywords. Mercury, gold mining, borax, Zimbabwe Nadine Steckling J Health Pollution 7: 54-61 (2014) University Hospital Munich Ziemssenstr. 1, D-80336 Munich, Germany “Minamata Convention on Mercury” The implementation of mercury- Tel + 0049-89-4400-53244 prepared by the UNEP (United free or at least mercury-restricted [email protected] Nations Environment Programme) gold mining technologies is urgently was finalized in October 2013 in needed to protect the biophysical Kumamoto, Japan. The convention will environment and human health.3-6 be a global, legally binding instrument Nevertheless, a new technology needs as soon as it is ratified by a majority of to be very convincing for miners UNEP member countries. In Article to quit their traditional, easy, and Introduction 7 and Annex C of the convention, effective amalgamation technology.7-9 specific tasks are mentioned in A currently promising, but not fully Mercury is extensively used in connection with ASGM: “Each Party developed technique is the use of artisanal small-scale gold mining that has” ASGM “and processing borax.10 Borax is applied as a to (ASGM) in more than 70 countries subject to this Article within its reduce the of gold dust worldwide.1 The international territory shall take steps to reduce, and contained in grinded ore; thus, after a community has identified and where feasible eliminate, the use of direct smelting process, very pure and specified mercury as an extremely mercury and mercury compounds in, mercury-free gold is the result.11,12 hazardous chemical with harmful and the emissions and releases to the effects to human health and the environment of mercury from, such Borax is a naturally occurring biophysical environment. Thus, the mining and processing”.2 and can be mined. It is used in many

54 Journal of Health & Pollution Vol. 4, No. 7 — October 2014 Steckling et al Case Study Introduction of a mercury-free gold extraction method using borax in Zimbabwe

products like soap or in industry, Abbreviations e.g. as a flux in .13 Borax is not considered to be an acutely toxic ASGM Artisanal small-scale DIN EN Norm for graphical symbols for substance. Although borax exposure gold mining ISO 10628 process plants (issued by the in air, which is the pathway of interest German Institute for in the gold mining process, can be Au Gold Standardization, DIN; the associated with mild irritation of the European Committee for eye, throat, and nose, it is not thought BMUB German Federal Ministry Standardization, EN (European to cause cancer. Animal studies for the Environment, Standard); the International have suggested that high exposure Nature Conservation, Organization for to is related to reproductive Building, and Nuclear Safety Standardization, ISO) toxicity, but there is no evidence for 13,14 humans. However, the ingestion Cu Copper GMP Global Mercury Project of large amounts of boron (e.g. 30 13 grams of ) may be fatal. In H 0 Water summary, the borax method can be 2 a safer alternative to mercury in gold Hg Mercury extraction.14 UNEP United Nations In the Benguet area of the , Environment Programme borax is traditionally used in ASGM.15 The method was tested and introduced in Tanzania,12,15,16 Ghana,7 Mongolia,17 and Sumbawa in Indonesia18 with good results. In Kalimantan (), the method failed because of the peculiar cases, hammers are used to crush big collect in a centrifuge through a pipe ore mineralogical composition.9,19 boulders before bringing the ore in starting at the end of the copper plate. wheelbarrows to the mill (step 3, Figure Residual gold contained in the pulp is Current gold mining and processing 1). The ore is crushed by the stamp concentrated by the rotating centrifuge practice in Kadoma mill (step 4, Figure 1) (Web Figure 2) (step 7, Figure 1) (Web Figure 4); In the Kadoma area, mercury which may be powered by an electric before further panning (step 8a, Figure amalgamation is the technology of generator or connected to grid power. 1) and squeezing in a cloth (step 9a, choice in ASGM.20-23 The fourteen Water is added to the milled ore (step Figure 1) to produce a final solid piece steps typical of the current gold 5, Figure 1) and the resulting pulp is of which is then transported mining and processing practice in then flushed over a sieve grid in order to the smelting place (step 10a, Figure Kadoma are depicted in Figure 1. to catch residual oversized ore particles 1). Over a piece of burning Currently, ASGM in Kadoma begins (Web Figure 3). or firewood step( 11a, Figure 1), the with digging for the ore (step 1, amalgam piece is smelted (step 12a, Figure 1). The ore is collected from The pulp is further flushed down over Figure 1) (Web Figure 5). The mercury underground gold mines (Web Figure a mercury covered copper plate (step in the amalgam vaporizes (step 13a, 1 in the Supplemental Material). 6, Figure 1). The gold contained in the Figure 1) and the gold (with residual Dynamite is commonly used to blast pulp binds onto the mercury on the mercury) is the result (step 14a, the rocks. The miners performing copper plate. At the end of the flushing Figure 1). these functions are referred to as procedure, the worker scrapes the diggers and blasters. The ore is copper plate with a rubber scrubber Beyond the copper plate and manually carried to the surface. to collect the gold-mercury amalgam centrifuge, the , containing which is later further concentrated residual gold as well as mercury The ore is transported to a custom through panning (step 8a, Figure 1) or other added components, are milling centre, which is normally a and squeezed in a special cotton silky piped into a tailings dam. However, central point where the miners from cloth to remove excess mercury from the tailings are further processed surrounding mines bring their ore the amalgam before smelting (step through a cyanidation process by for milling (step 2, Figure 1). In some 9a, Figure 1). The overflow pulp may the miller (step 8b to 10b, Figure 1)

55 Steckling et al Journal of Health & Pollution Vol. 4, No. 7 — October 2014 Case Study

Figure 1 — Technical drawing of current borax gold processing method

and 2). Within an 8-24 hour cycle, hazard in the area,21 especially for demonstrate the mercury-free gold the residual gold is dissolved by the children,24 as results from the Global extraction technology using borax. cyanide to form a pregnant solution. Mercury Project (GMP) showed.20 The pregnant solution is exposed to It is therefore imperative and urgent Materials and Methods active carbon columns which adsorb to introduce mercury-free gold the gold (step 11b, Figure 1). The gold extraction techniques in Kadoma and Zimbabwe was selected as a project loaded carbon columns eventually other gold mining areas in Zimbabwe country because of the high mercury release the adsorbed gold onto wire and globally. release due to ASGM, with an wool which is ultimately burned to estimated 25 tons of mercury used obtain the pure gold (step 12b, Objectives in the sector annually.25,26 Thus, figure 1). A successful introduction of the Zimbabwe belongs to the top 10 borax method depends on the local mercury emitters due to ASGM An important aspect of this conditions and has been shown in worldwide.1 It is estimated that 10% methodology is that mercury is added previous studies.7,11,12,15,16,19 Therefore, of the gold produced by ASGM in to the ore pulp before concentration the objective of the project was to Zimbabwe is produced in Kadoma,26 rather than to a concentrate. This is test if gold extraction using borax which underscores the choice of what is referred to in the literature is possible in Kadoma. Is the ore the region. Additionally, Kadoma is as ‘whole ore amalgamation’ and is suitable for extracting gold using known to the authors due to their believed to result in the loss of a lot of borax? Are the equipment and participation in the GMP.25 The mercury to the environment.8 materials necessary for the borax contact between the partners from method available in Kadoma? Are Zimbabwe and Germany has never In the Kadoma area, the use of the miners interested in embracing been broken since 2002, when the whole ore amalgamation is very the borax method instead of GMP started. The call for a mercury- common.20 Mercury is therefore a amalgamation? A field project in free mining technology came from the serious environmental and health Kadoma/Zimbabwe was done to local partner in Zimbabwe.

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Figure 2 — Technical drawing of the new borax gold processing method demonstrated in the field project in Kadoma, Zimbabwe

The local conditions for the implementation, a German engineer Web Table 1, included enough time for introduction of a mercury-free gold (Stefan Muschack) was responsible for discussion, questions, and answers. extraction method in Kadoma were technical support and documentation tested in terms of (a) acceptance by by photographs and videos, while the All equipment and material was the locals, (b) availability of equipment partner in Zimbabwe (Dennis Shoko) sourced in and around Kadoma town. and materials, and (c) suitability of the organized the field phase. International The demonstration was conducted ore. The results, based on discussions experts in the borax method were at the Tix and Venture mills, while and observations as well as by trial and invited to join the field phase, but the smelting was done in Kadoma town. error, were documented on the spot in limited time frame hindered their the form of notes, pictures, and videos. participation. However, they promoted The project did not compare the project success by providing written borax and amalgamation methods. The project consisted of a preparation and audio-visual information used Conclusions regarding recovery rates, phase (September until early in addition to the existing published costs, ease of use, or time required December 2013) and a field phase, material.8,11,15,16,27,28 for the borax (and/or amalgamation) including a one-day theoretical method(s) are beyond the paper’s workshop and a two-day practical The theoretical workshop took place scope. Consequently, a comprehensive field-based demonstration, conducted at Kadoma Sports Club and was demonstration of the new method, on the 4th to the 6th of December organized to inform and theoretically including verifiably convincing the 2013 in Kadoma. The project team educate the local miners and miners to change to the method consisted of German scientists stakeholders about the project, proving would be a next well-prepared step from the University Hospital the need for mercury-free methods, after the successful testing. During the Munich (Nadine Steckling, Stephan to introduce the borax method, and December 2013 short demonstration Bose-O'Reilly, Rudolf Schierl), to get feedback from the miners about project, there was neither the time who organized the overall project the acceptability of a new technology. nor the financial resources to conduct preparation, coordination, and Every point of the agenda, listed in a survey or to collect heath and/or

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The next step involved the regular washing of the artificial turf in a container full of water to wash the ore concentrate out of the turf (Figure 3, right, step 8a, Figure 2). A second string of ore concentrate was collected in the centrifuge beyond the sluice box (step 7, Figure 2) and also collected in the water container (step 8a, Figure 2). The water-ore mixture was taken out of the water container and repeatedly panned in a washing plate to rid the concentrate of light waste (step 9a, Figure 2). The heavier gold and other heavy mineral particles were mechanically concentrated. To improve the separation of gold and other minerals, soap was added to Figure 3 — Sluice box reduce the surface tension (Web Figure 8). The resultant concentrate contained a visible high percentage of gold dust.

biomonitoring data. The scope of the on their own. These positive indices The panning process took a lot of project was limited to a short field- convinced the project team that the time, resulting in time pressure. The

based demonstration of the borax miners were interested and that they efficiency of the panning process method, which was realized by the were willing to change to a mercury- was called into question when one use of simple methods (observations, free technology. of the gold miners panned a part of discussions, and trial and error). the residual ore once again resulting The practical demonstration started in another visible amount of gold Results with purchasing the necessary material dust. The second recovery of fine and equipment. While borax, plastic gold showed that the panning process Fifty invited locals (miners and bags, and soap were easily obtainable, needed refining to make it more officials of ministries and agencies) the availability of carpets and blow efficient. Further panning was not listened carefully to the lectures and torches was very limited (Web Table possible within the limited project videos at the theoretical workshop, 2). Finally, an artificial turf was used timeframe. Consequently, the tailings asked questions, and reported as a carpet substitute and a blow torch were discarded after the second run experiences (Web Figure 6). They was rented in Kadoma town, several concentrate was recovered. were especially interested in the kilometers away from the mills. differences between amalgamation and In the next step, a magnet was used to the borax method, the applicability of The main steps of the new method are remove a large amount of from borax by use of available equipment depicted in Figure 2. the concentrate (probably wear and (e.g. mills), the availability, price, tear from the ) (Web Figure and required quantity of borax, as The mined ore was milled and mixed 9). Nitric acid was added to eliminate well as possible health effects due with water (steps 1 to 5, Figure 2) the remaining impurities. The final to mercury compared to borax. before entering the provisional sluice concentrate was stored under water in During the workshop they asked for box (step 6, Figure 2). The artificial turf a plastic bag (Web Figure 10), which demonstrations of the borax method (carpet substitute) was cut and sized was taken back to Kadoma town and 30 to 40 of them spontaneously to fit onto the copper plate to create (step 10a, Figure 2) where blow torch decided to take part in the subsequent a sluice box (Figure 3). Adjustments services were available (step 11a, Figure practical demonstration (Web Figure to the length and inclination angle 2). This stage involved the mixing of 7). They invested two further days and of the sluice box would improve the the concentrate with an equal amount organized transport to the testing sites processing conditions (Web Table 2). of borax and some water (Web Figure

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11). This mixture was smelted with a concentrate during the panning stage. expected, but needs to be verified by blow torch in a bowl (steps This was due to the fact that although multiple testing.9 11a to 13a, Figure 2) (Web Figure 12). the mills were cleaned before the borax was added to the smelted mixture demonstrations, the environment 3. Demonstration: The effectiveness to produce a well-shaped 1.11 gram and the existing equipment remained of the borax method needs to be gold button (step 14a, Figure 2) (Web contaminated. Nevertheless, the demonstrated for the miners, either Figure 12). mercury was not needed to obtain the by comparing both methods or gold in this project. by applying the borax method to On the first demonstration day at Tix tailings of the amalgamation process. mill, a local gold miner provided a Currently, the millers make their Consequently, the gold lost due to part of his ore for the demonstration. money by applying cyanidation to the their highly polluting traditional After concentrating the ore by use tailings, obtaining a significant part technology would be visualized. of the artificial turf and a washing of residual gold (see steps 8b to 12b A mobile demonstration unit is plate (until step 9a, Figure 2), the local in Figures 1 and 2). Improving the recommended to reach as many miner noticed more fine grained gold milling process and implementing miners as possible. particles than were captured by the carpet sluice boxes to concentrate traditional amalgamation process. The the ore mechanically and more 4. Convincing and winning over the trial was stopped by the ore owner efficiently might result in more gold miners: Although the demonstration after observing the fine gold particles for the miners and less gold for the was of a very experimental nature and in the concentrate. He decided to millers. This could be a source of short duration, the results appeared proceed rapidly to amalgamate rather conflict between miners and millers. to have convinced the miners that the than wait for the borax method which It is therefore necessary to design the borax method works, as perceived was going to require blow torch project demonstrations in such a way by the project team. Nevertheless, services back in Kadoma town, about that conflicts are avoided in order to the perception of the project team twenty kilometers away. Subsequently, ensure success and wider acceptance needs to be statistically verified. The the project team decided to buy half of the new technology. It is also likely conviction and acceptance of the a ton of ore from a local miner at that the new technology may require new methodology by the miners will Venture mill. This enabled the entire some technology change in milling have to be tested thoroughly after an process, starting with ore and resulting as well. optimization of the borax method. in gold, without any interference. Recommendations 5. Assessment: There is a risk that the Conclusion Following this successful pilot project, miners may not change from mercury there remains a need for follow-up amalgamation to the borax method The demonstration project proved that implementation activities in support of entirely, but that they may apply a mercury-free gold winning method the borax method in Zimbabwe. both techniques side by side. It will using borax and a carpet-covered therefore be necessary to monitor sluice box is feasible in Kadoma, 1. Optimization: The borax method the success of the “phasing out” of Zimbabwe resulting in 1.11 grams of needs to be optimized in the field (see mercury amalgamation by testing gold from 500 kg of ore. The project Web Table 2). The optimal material the mercury exposure of miners in team noticed a huge interest from and equipment (e.g. effective mills, human biomonitors and to survey the miners in the borax method. The more suitable carpets, longer sluice the health situation of the miners as borax pilot project was very successful boxes) available or acceptable in the well as their knowledge, attitudes, and and encouraging and should hopefully region needs to be determined. practice (KAP). pave the way to the phasing out of the use of mercury in gold mining and 2. Comparison: A direct comparison The above interventions are processing in Zimbabwe. of the optimized borax method essential for future projects to and the common amalgamation ensure a successful and sustainable Although the once-off primary pilot procedure regarding costs, gold introduction of the borax method in project had a very experimental recovery, practicability, and time ASGM in Zimbabwe. Follow-up work character, largely mercury-free gold efficiency is necessary. A higher coupled with the expected restriction was the result. The miners noticed output by the borax method in of mercury availability following the small mercury particles in the comparison to amalgamation can be expected ratification of the Minamata

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Convention may eventually provide [Internet]; 2013 Oct 10 - 11; Kumamoto, Japan. mercury-free gold processing for artisanal and the sway in favour of mercury-free Nairobi, Kenya: United Nations Environment small-scale gold miners in Ghana. Int J Environment technologies. A very valuable add- Programme (UNEP); 2013 [cited 2014 Jul 7]. 30 p. Pollut [Internet]. 2010 [cited 2014 Jul 13];42(3/4):289- on for future studies would be the Available from: http://www.mercuryconvention.org/ 303. Available from: http://nora.nerc.ac.uk/9990/1/ consideration of other health risks in Portals/11/documents/conventionText/Minamata%20 IJEP_0010_Styles_et_al_final_.pdf mining other than mercury, e.g. toxic Convention%20on%20Mercury_e.pdf 11. Appel PW, Na-Oy L. The borax method of gold 29,30 cyanide. 3. UNEP. Mercury: Time to act [Internet]. Nairobi, extraction for small-scale miners. J Health Pollut Kenya: United Nations Environment Programme [Internet]. 2012 Jun [cited 2014 Jul 13];2(3):5-10. This project demonstrates that (UNEP); 2013. [cited 2014 March 2]. 44 p. Available Available from: http://www.journalhealthpollution. mercury-free technologies are from: http://www.unep.org/PDF/PressReleases/ org/doi/pdf/10.5696/2156-9614-2.3.5 available and that miners are able Mercury_TimeToAct.pdf 12. Appel PWU, Na-Oy L. How to mitigate mercury and willing to use them. This is in 4. Kirby T. UN agrees new treaty to reduce pollution in Tanzania. J Environ Prot [Internet]. 2013 accordance with the “Minamata harm from mercury [Internet]. Lancet. 2013 Feb May 21 [cited 2014 Jun 13];4(5A):1-5. Avilable from: Convention”, in which Article 7 calls 2 [cited 2014 Jul 7];2(381):362. Available from: http://www.blacksmithinstitute.org/files/FileUpload/ for: “Use of existing information http://www.thelancet.com/pdfs/journals/lancet/ files/Appel%20&%20Na-Oy%20Tanzania.pdf exchange mechanisms to promote PIIS0140673613601531.pdf 13. U.S. Department of Health and Human Services. knowledge, best environmental 5. Kristensen AK, Thomsen JF, Mikkelsen .S A Toxicological profile for boron [Internet]. Atlanta, practices and alternative technologies review of mercury exposure among artisanal small- Georgia: Agency for Toxic Substances and Disease that are environmentally, technically, scale gold miners in developing countries [Internet]. Registry; 2010 Nov [cited 2014 Jul 13]. 197 p. 2 socially and economically viable.” Int Arch Occup Environ Health. 2013 Aug 27 [cited Available from: http://www.atsdr.cdc.gov/toxprofiles/ 2014 Jul 7]. Available from: http://link.springer.com/ tp26.pdf Acknowledgements. article/10.1007/s00420-013-0902-9 Subscription 14. Riederer A, Caravanos J. Borax - summary of All miners and millers involved and required to view. ISSN: 1432- 1246. health risks associated with using borax in artisanal all participants in the workshop and 6. Schmidt CW. Quicksilver and gold: mercury and small-scale gold mining [Internet]. New York:

field demonstrations are gratefully pollution from artisanal and small-scale gold mining. Institute; 2013 Apr 1 [cited 2014 Jul 13]. acknowledged. Special thanks go to Environ health perspect [Internet]. 2012 Nov [cited 6 p. Available from: http://www.blacksmithinstitute. Evans Ruzvidzo and Oliver Phiri (both 2014 Jul 7];120(11):A424-9. Available from: http:// org/files/FileUpload/files/Borax%20in%20ASGM%20 Zimbabwean Artisanal and Small www.ncbi.nlm.nih.gov/pmc/articles/PMC3556620/ Final%20-%20April%201%202013.pdf Scale Miners Association members). 7. Amankwah RK, Styles MT, Nartey RS, Al- 15. Appel PW, Jonsson JB. Borax – an alternative to Peter Appel and Erik Joers receive a Hassan S. The application of direct smelting of mercury for gold extraction by small-scale miners: special thank you for their intellectual gold concentrates as an alternative to mercury introducing the method in Tanzania. Geol Surv support. Without the involvement amalgamation in small-scale gold mining operations Denmark Greenland Bull [Internet]. 2010 [cited 2014 of local partners, the project would in Ghana. Int J Environ Pollut [Internet]. 2010 [cited Jul 13];20:87-90. Available from: http://www.geus.dk/ not have been possible. Funding by 2014 Jul 7];41(3/4):304-15. Available from: http:// publications/bull/nr20/nr20_p087-090.pdf the German Federal Ministry for the www.inderscience.com/info/inarticle.php?artid=33238 16. AGENDA. Training of trainers on alternatives Environment, Nature Conservation, Subscritpion required to view. of mercury and best available techniques (BATs) and Building, and Nuclear Safety (BMUB) 8. UNEP. A pracitcal guide: reducing mercury use best environmental practices (BEPs) in artisanal and is gratefully acknowledged (reference in artisanal and small-scale gold mining [Internet]. small scale mining in Tanzania (Phase III) [Internet]. number 03032/1/2013). Nairobi, Kenya: United Nations Environment Dar es Salaam, Tanzania: AGENDA for Environment Programme (UNEP); 2011 [cited 2014 March and Responsible Development; 2010 Jul [cited 2]. 81 p. Available from: http://www.unep.org/ 2014 March 2]. 27 p. Available from: http://www. chemicalsandwaste/Portals/9/Mercury/Documents/ zeromercury.org/phocadownload/Whats_on_in_the_ ASGM/Techdoc/LAST%20VERSION%20UNEP_ regions/ASGM_Borax_Training_Report-20102.pdf References Technical_Document__DEC_31_E[1].pdf 17. SDC experiences with formalization and 9. Appel PW, Na-Oy LD. Mercury-free gold responsible environmental practices in artisanal and 1. Telmer KH, Veiga MM. World emissions extraction using borax for small-scale gold miners. small-scale gold mining in Latin America and Asia of mercury from artisanal and small scale gold J Environ Prot [Internet]. 2014 May [cited 2014 Jul (Mongolia) [Internet]. Switzerland: Swiss Agency mining. In: Pirrone N, Mason R, editors. Mercury 13];5:493-9. Available from: http://www.geus.dk/DK/ for Development and Cooperation; 2011 [cited fate and transport in the global atmosphere: emissions, int_devel_projects/Documents/mercury-free_gold_ 2014 Jul 13]. 58 p. Available from: http://www.sdc- measurements and models. Dordrecht: Springer extraction_using_borax_jep_2014.pdf employment-income.ch/en/Home/News/media/e%20 Science+Business Media; 2009. p. 131-72. 10. Styles MT, Amankwah RK, Al-Hassan S, Nartey und%20i%20net/SAM%20booklet.pdf 2. UNEP. Minamata convention on mercury RS. The identification and testing of a method for 18. Blacksmith Institute. First successful

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