Mineral Journal · 2016. 9. 1. · Science and Technology Development and the Ministry of Mines and...

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Issue 2

September - December 2014Beneficiation & Value addition

Mineral Beneficiation Value Addition

Mineral Beneficiation & Value Addition 2Design Editor - Shadreck Gurenje 0772946310 / 0716426767 email [email protected]

The articles in this issue are being published with the primary and principal objective of promoting local mineral value addition by identifying value-added products that are made from the country’s minerals.

In the majority of cases these value added products are manufactured in countries where Zimbabwe exports raw concentrates to. The ultimate objective of full value-addition is to produce products that fetch a premium in their markets, create jobs, grow the economy and ultimately lead to a better quality of life for all in Zimbabwe.Ed

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Professor Francis P Gudyanga permanent secretary Ministry of Mines & Mining Development

Mineral Beneficiation & Value Addition 3

Contents

Bioleaching


Zimbabwe is richly endowed with numerous refractory gold ore deposits. In or-

der to render the refractory gold amenable to cyanide leaching, the ore has to be pre-treated to de-compose the sulphide and other accompanying host minerals. Tra-ditionally, this has involved an oxi-dative treatment that is either ther-mal, biological or chemical.

In this respect, the most com-mon pre-cyanidation treat-ments are roasting, pressure

leaching, chemical oxidation at atmospheric pressure, chlorination and bioleaching. The mineralogy of the ore usually determines the pre-treatment process that will re-sult in maximum gold recovery.Bioleaching is a simple and ef-fective technology for metal ex-traction from low-grade ores and mineral concentrates. Metal recovery from sulfide min-erals is based on the activity of chemolithotrophic bacteria, main-ly Thiobacillusferrooxidans and T. thiooxidans, which convert insolu-ble metal sulfides into soluble met-al sulfates. Non-sulfide ores and minerals can be treated by heterotrophic bac-teria and by fungi. In these cases metal extraction is due to the pro-duction of organic acids and che-lating and complexing compounds excreted into the environment. At present bioleaching is used es-sentially for the recovery of copper, uranium and gold, and the main techniques employed are heap, dump and in situ leaching. Tank leaching is practised for the treat-ment of refractory gold ores. Bioleaching has also some po-tential for metal recovery and de-toxification of industrial waste products, sewage sludge and soil contaminated with heavy metals.

It is also used for the recovery of metals such as copper, zinc, lead, arsenic, antimony, nickel, molyb-denum, gold, silver, and cobalt from refractory ores.Bioleaching can involve numerous ferrous iron and sulfur oxidizing bacteria, including Acidithiobacil-lusferrooxidans and Acidithioba-cillus (formerly known as Thioba-cillus). As a general principle, Fe3+ ions are used to oxidize the ore. This step is entirely independent of microbes. The role of the bacteria is the fur-ther oxidation of the ore, but also the regeneration of the chemical oxidant Fe3+ from Fe2+. For ex-ample, bacteria catalyse the break-down of the mineral pyrite (FeS2) by oxidising the sulfur and metal (in this case ferrous iron, (Fe2+)) using oxygen. This yields solu-bleproducts that can be further purified and refined to yield the desired metal.Pyrite leaching (FeS2):In the first step, disulfide is sponta-neously oxidized to thiosulfate by ferric ion (Fe3+), which in turn is reduced to give ferrous ion (Fe2+):(1) spontaneousThe ferrous ion is then oxidized by bacteria using oxygen:(2) (iron oxidizers)Thiosulfate is also oxidized by bac-teria to give sulfate:(3) (sulfur oxidizers)The ferric ion produced in reac-tion (2) oxidized more sulfide as in reaction (1), closing the cycle and given the net reaction:(4) The net products of the reaction are soluble ferrous sulfate and sul-furic acid.The microbial oxidation process occurs at the cell membrane of the bacteria. The electrons pass into the cells and are used in biochemi-

cal processes to produce energy for the bacteria while reducing oxygen to water. The critical reaction is the oxidation of sulfide by ferric iron. The main role of the bacterial step is the regeneration of this reactant.The process for copper is very sim-ilar, but the efficiency and kinetics depend on the copper mineralogy. The most efficient minerals are su-pergene minerals such as chalcoc-ite, Cu2S and covellite, CuS. The main copper mineral chalcopyrite (CuFeS2) is not leached very effi-ciently, which is why the dominant copper-producing technology re-mains flotation, followed by smelt-ing and refining. The leaching of CuFeS2 follows the two stages of being dissolved and then further oxidised, with Cu2+ ions being left in solution.Chalcopyrite leaching:(1) spontaneous(2) (iron oxidizers)(3) (sulfur oxidizers)net reaction:(4) In general, sulfides are first oxi-dized to elemental sulfur, whereas disulfides are oxidized to give thio-sulfate, and the processes above can be applied to other sul-fidic ores. Bioleaching of non-sulfidic ores such as pitchblende also uses ferric iron as an oxi-dant (e.g., UO2 + 2 Fe3+ ==> UO22+ + 2 Fe2+). In this case, the sole pur-pose of the bacterial step is the regeneration of Fe3+. Sulfidiciron ores can be added to speed up the process

Bioleaching


and provide a source of iron. Bi-oleaching of non-sulfidic ores by layering of waste sulfides and ele-mental sulfur, colonized by Acid-ithiobacillus spp., has been accom-plished, which provides a strategy for accelerated leaching of materi-als that do not contain sulfide min-erals.[2]Traces of precious metals such as gold may be left in the original solution. Treating the mixture with sodium cyanide in the presence of

free oxygen dissolves the gold. The gold is removed

from the solution by adsorbing (taking it

up on the surface) to charcoal.

Extractions in-volve many

e x p e n s i v e steps such as roasting

and smelt-ing, which re-

quire sufficient concentrat ions

of elements in ores and are environmen-

tally unfriendly. Low concentrations are not

a problem for bacteria because they simply ignore the waste that surrounds the metals, attaining extraction yields of over 90% in some cases. These microorganisms actually gain energy by breaking down minerals into their constitu-ent elements. The company simply collects the ions out of the solution after the bacteria have finished. There is a limited amount of ores.Bioleaching is in general simpler and, therefore, cheaper to operate and maintain than traditional pro-cesses, since fewer specialists are needed to operate complex chem-icalplants. The process is more en-vironmentally friendly than tradi-tional extraction methods. For the company this can translate into profit, since the necessary limiting of sulfur dioxideemissions during smelting is expensive. Less land-scape damage occurs, since the bac-teria involved grow naturally, and the mine and surrounding area can be left relatively untouched. As the bacteria breed in the conditions of the mine, they are easily cultivat-ed and recycled. Bioleaching can be used extract metals from ores that are too poor for other tech-

nologies. It can be used to partially replace the extensive crushing and grinding that translates to prohibi-tive cost and energy consumption in a conventional process.The bacterial leaching process is very slow compared to smelting. This brings in less profit as well as introducing a significant delay in cash flow for new plants. Toxic chemicals are sometimes produced in the process. Sulfuric acid and H+ ions that have been formed can leak into the ground and sur-face water turning it acidic, caus-ing environmental damage. Heavy ions such as iron, zinc, and arsenic leak during acid mine drainage. When the pH of this solution rises, as a result of dilution by fresh wa-ter, these ions precipitate, forming “Yellow Boy” pollution. For these reasons, a setup of bi-oleaching must be carefully planned, since the process can lead to a biosafety failure. Unlike other methods, once started, bio-heap leaching cannot be quickly stopped, because leaching would still continue with rainwater and natural bacteria.


Minerals processing and beneficiation is an area of immense potential and growth for all the nations worldwide,

especially those which are endowed with na-ture’s blessings in the form of abundant mineral resources. The mining industry has also been crucial to the economic development in both historical and contemporary terms and the min-ing sector is both a major employer and a major contributor to the export revenues. Unfortunate-ly, these resources are not fully exploited in de-veloping countries due to the lack of advanced skills, modern and i n n o - v a -

tive research and tech-nology and the new world trade regime. Many minerals are still exported as ores, concentrates or metals, without significant downstream pro-cessing or value addition. Therefore there is an urgent need for the policy makers, scientists, technologists, academics and other industry experts to come together and assess ways and means to address the aforementioned skills gap. 2. The Centre for Science & Technology of the Non-Aligned and Other Developing Countries (NAM S&T Centre) had earlier organized two international programmes on Minerals, the first one being the International workshop on ‘Min-eral Resources and Development’ in July 2004 at

Kerman, Iran in association with Shahid Bahonar University of Kerman.

The second one was the In-ternational Workshop

on ‘Minerals Pro-cessing and Benefi-

ciation’ organized in September 2012 in Johan-nesburg, South Africa jointly with the Depart-

ment of Science and Technology of

South Africa, which got concluded with the adoption

of a Resolution having a number of significant recommendations for various countries and

stakeholders. It also strongly urged to hold sim-ilar scientific programmers in other developing countries for strengthening and promoting the relations among various countries on Minerals Processing and Beneficiation 3. As a follow up, the NAM S&T Centre orga-nized its 3rd International Workshop on ‘Miner-al Processing and Beneficiation’ at Harare, Zim-babwe during 11-14 September 2014 jointly with the Ministry of Higher and Tertiary Education, Science and Technology Development and the Ministry of Mines and Mining Development of the Republic of Zimbabwe for brainstorming by international policy makers, scientists and tech-nologists, mining industry executives, mineral

industry and technology producers, investors, exploration people, mine owners and trad-

ers, planners and decision-makers. 4. The Workshop was inaugurated by His Excellency Robert G. Mugabe, The President and Head of State and Government of the Republic of Zim-babwe on 11th September 2014 in a glittering ceremony before the gath-ering of over 1000 foreign delegates and Zimbabwean Ministers, Members

of Parliament, senior government offi-cials, mineral experts and professionals,

faculty members and students. After the welcome remarks by Dr. W T Mbi-

zvo, Permanent Secretary, Ministry of Higher & Tertiary Education, Science and Technology De-velopment (MHTESTD).H Dr. O.N. Muchena, MP and Honorable Min-ister of MHTESTD, Zimbabwe in her remarks welcomed the His Excellency President Mugabe and thanked the NAM S&T Centre for bestow-ing the honor to Zimbabwe to host the import-ant workshop with wide range of papers for the benefits of developing countries through S&T including human capacity building in Minerals Processing and Beneficiation. She mentioned that the Science, Technology and innovation Policy of Zimbabwe was launched in 2012 with six primary goals, one of these being South-South Cooperation. She then introduced Presi-dent Mugabe to the audience. This was followed by short remarks by Hon.Chidakwa, MP and Honorable Minister of Mines and Minerals De-velopment, Zimbabwe. The Deputy Minister of MHTESTD, Dr. G. Gandawa, MP handed over the First Award of ‘The Scientist of the Year 2014’ to President Mugabe for his outstand-ing contribution to Education and Science and Technology.

His Excellency President Mugabe in his address, while describing the historical background of the Non-Aligned Movement (NAM) fondly remembered his personal association with the former Indian Prime Ministers, Indira Gandhi and Rajiv Gandhi and said that the NAM had played a vital role in the global political sce-nario in bringing peace under the backdrop of the Cold War between the USA and the Sovi-

NAM Report on the 3rd International workshop on mineral processing and beneficiation


NAM Report on the 3rd International workshop on mineral processing and beneficiation et Union. He said that it is worrying that the importance of the NAM has diminished po-litically at the moment and emphasized that the unity among the NAM member countries should form the basis to contain the present day economic dominance of the USA and the European Union across the globe. He desired that the NAM countries should join them-selves together through trade and value addi-tion to their natural resources and transform the movement into an economic power house. The President noted that the desire of the founding members of the Non-Aligned Move-ment for the exchange of information, trade and statistics was realized through the estab-lishment of the South-South Centre in Geneva and added that the setting up of the NAM S&T Centre was another initiative in this direction. He commended the NAM S&T Centre for coming out with a platform for the exchange of information and expertise in Science and Technology in the spirit of South-South Coop-eration. He further complimented the Centre for taking up such an appropriate subject like Minerals Processing and Beneficiation which is of prime importance to the NAM Countries, particularly the African nations. He observed that the developing countries have so far been engaged in minerals exploration and ex-traction and exporting the same as raw materi-als and hoped that the workshop would be able to address the need for the flow of knowledge and understanding the best practices in bene-ficiation and value addition of such resources.

The President offered to host a Non-Aligned Movement Science & Technology Centre of Excellence on Minerals Processing and Ben-eficiation in Zimbabwe for the benefit of the member states and the development of back-ward and forward linkages in the field. He then declared open the International Work-shop and also launched a journal on Minerals Beneficiation and Value Addition. 5. The Workshop was attended by 110 par-ticipants from 15 countries, including Af-ghanistan, Guyana, Indonesia, Iran, Malaysia, Mauritius, Myanmar, Nigeria, South Africa, Sri Lanka, Tanzania, Uganda, Vietnam, Zam-bia and Zimbabwe of which 89 delegates were from the host country Zimbabwe. The organiz-ing team comprised 3 representatives from the NAM S&T Centre and several officials from the host country, most of who also actively joined the workshop deliberations. The overseas participants were from Af-ghanistan [Mr. Popal Faizi, Head of Minerals Team, Ministry of Mines]; Guyana [Ms. Di-anne A McDonald, Snr. Mineral Processing Engineer II, Head-Mineral Processing Unit of Guyana Geology & Mines Commission]; Indonesia [Mr. YohannesYudiPrabangka-ra, Director, Centre for Mineral Resources Technology, The Agency for the Assessment and Application Technology (BPPT)]; Iran

[Engr. Mr. MortezaRastegaran, Representa-tive of CITC in Harare and Attaché (Science & Technology) of the Embassy of I.R. of Iran in Harare]; Malaysia [Mr. MalekSelamat, Se-nior Research Officer, Mineral Research Cen-tre, Minerals and Geoscience Department]; Mauritius [Dr. GoodaryRajeshwar, Dean and Head, Faculty of Sustainable Development and Engineering. Head of Geotechnical Lab-oratory/Lecturer -Soil Mechanics, Université des Mascareignes (Ex-IST)]; Myanmar [Mr. KhinMaungHtwe, Associate Professor, Head of Department (Mining Engineering), Tech-nological University (Taunggyi), Ministry of Science and Technology]; Nigeria [Mr. Oluse-gun Adewole, Deputy Director, Raw Materials Research and Development Council, (Federal Ministry of Science and Technology); South Africa [Ms. MohaleSetepane, Chief Director: Mineral Promotion and International Coor-dination, Department of Mineral Resources] and [Mr. Tony Nyakudarika, Principal Pro-cess Engineer, DRA Projects (Pty) Ltd, South Africa] and [Mr. Brighton Gwavava, Manag-ing Director, Suntech Geometallurgical Lab-oratories] and Mr. Joel Mungoshi, Director and Principal Consultant, Manhize Projects]; Tanzania [Ms. Tabitha Geoffrey Etutu, Depart-ment of Science and Technology, Ministry of Communication, Science and Technology]; Uganda [Mr. Richard Tushemereirwe, Senior Presidential Advisor for Science, State House]; Vietnam [Mrs. Vu Anh Thu, Lecturer, Depart-ment of Geology, Faculty of Geology, Hanoi University of Mining-Geology]; Zambia [Dr. Lordwell. K. Witika, Department of Metallur-gy and Mineral processing, School of Mines, University of Zambia]; Zimbabwe [Prof. D. J. Simbi, Vice Chancellor, Chinhoyi University of Technology] and [Mr. Louis Mabiza, Gen-eral Manager-Processing, Zimplats] and [Prof. C.C. Maponga, Technical Director-Nanotech-nology, Ministry of Higher and Tertiary Edu-cation, Science and Technology Development] and [Dr. Elias Matinde, Director-Metallurgical Research, Scientific and Industrial Research and Development Centre (SIRDC)] and [Mr. RabbsonMpofu, Senior Assistant Commis-sioner, Officer Commanding Minerals and Border Control Unit].

6. The overall programme of the Workshop was conducted in seven Technical Sessions with three themes titled ‘Mineral Policies and Strategies in Developing Countries’, ‘Miner-al Resources in Developing Countries’ and ‘Technology Development in Mineral Process-ing and Beneficiation’, which were respectively cochaired by Mr. MalekSelamat (Malaysia), Mr. DedimuniSajjaha De Silva (Sri Lanka), Dr. Lordwell K. Witika (Zambia), Ms. Tabitha Geoffrey Etutu (Tanzania), Mr. Joel Man-goshi (South Africa), Dr. GoodaryRajeshwar (Mauritius), Mr. PopalFaizi (Afghanistan), Mr. Olusegun Adewole (Nigeria) and Mr.

Abel Moseki (South Africa), and Mr. Malcom Mazemo, Mr. MhanduTakunda and Mr. Itay-iMarufu of the host country Zimbabwe. The presentations made by the foreign partici-pants were on ‘Mining and Mineral Processing at Afghanistan’ by Mr. PopalFaizi of Afghani-stan; ‘Transitioning from Mercury based Gold Extraction to ‘No-Mercury’ Methods of Gold Extraction in the Guyana Gold Mining Sector’ by Ms. Dianne A McDonald of Guyana; ‘Arti-sanal and Small Scale Gold Mining in Indone-sia: Toward Mercury Free Gold Processing’ by Mr. YohannesYudiPrabangkara of Indonesia; ‘Mining Capacities in the Islamic Republic of Iran’ by Engr. Mr. MortezaRastegaran of Iran; ‘The Potential of Natural Malaysian Silica Sand to produce Leucite Glass-ceramics Suitable for Restorative Dental Applications’ by Mr. Malek-Selamat of Malaysia; ‘Minerals and Mineralo-gy in Mauritius’ by Dr. GoodaryRajeshwar of Mauritius; ‘Utilization of Mineral Resources in Myanmar’ by Mr. KhinMaungHtwe of Myan-mar; ‘Industrial Gap and the Mineral Industry in Nigeria’ by Mr. Olusegun Adewole of Nige-ria; ‘Mineral Policy Framework Beneficiation and Emerging Global Trends of Concern’ by Ms. MohaleSetepane and ‘Zimbabwe and the Platinum Group Metals (PGM) Value Chain’ by Mr. Tony Nyakudarika and ‘Recovery of Fine Diamonds by the GWASMF Process’ by Mr. Brighton Gwavava and ‘Process Options and Economics for the Beneficiation of Refrac-tory Gold Deposits in Zimbabwe’ by Mr. Joel Mungoshi of South Africa; ‘The Traditional Mineral Processing Methods in Sri Lanka and Future Prospects for Advance Mineral Pro-cessing and Beneficiation’ by Mr. Dedimuni Sajjaha De Silva of Sri Lanka; ‘Gasification of Municipal Solid Wastes in a Downdraft Gas-ifier: Solving Mining Energy Challenge’ by Ms. Tabitha Geoffrey Etutu of Tanzania; ‘Develop-ing Market Places and Commodity Exchanges for Minerals’ by Mr. Richard Tushemereirwe of Uganda; ‘Cost Benefit Analysis of Bauxite Exploitation in Tay Nguyen Area, Vietnam: Lessons for Industrial Mining in Developing Countries?’ by Mrs. Vu Anh Thu of Vietnam; ‘Fundamental Surface Properties of Carrollite (CoCu2S4) and its Flotation Behaviour’ by Dr. Lordwell K. Witika of Zambia. Five presentations were made by the Zimba-bwean participants, viz., ‘Wealth Creation for Sustainable Development: Towards Address-ing the Challenges in Human Capital Devel-opment in Minerals Processing and Benefici-ation’ by Prof. D. J. Simbi; ‘PGM beneficiation – Zimbabwe perspective’ by Mr. Louis Mabiza; ‘Minerals to Nanoparticles: The Role of Nan-otechnology in the Beneficiation and Value Addition of Minerals’ by Prof. C.C. Maponga; ‘Value Addition and Beneficiation: Developing A Capabilities Driven Beneficiation Frame-work for the Iron and Steel Industry in Zim-babwe’ by Dr. Elias Matinde; and ‘Zimbabwe Republic Police Min-

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erals and Border Control Unit (MBCU) in the Min-

ing Sector’ by Mr. Rabbson Mpofu. Prof. Arun Kulshreshtha, Director and Execu-tive Head of NAM S&T Centre made a presen-tation on ‘The Role of NAM S&T Centre for South-South Cooperation in Science & Tech-nology’. 8. Finally, the Concluding Session was co-chaired by Prof. Arun P. Kulshreshtha (NAM S&T Centre) and Mr. Richard Tushemereirwe (Uganda), in which the delegates extensively deliberated and debated on finalizing a doc-ument titled ‘Harare Declaration – 2014 on Mineral Processing and Beneficiation’ with a set of recommendations, which was thereaf-ter unanimously adopted by the participants and later presented to H.E. Dr. O.N. Muchena, MP and Honourable Minister of MHTESTD during the official banquet. 9. The Certificates for Participation were dis-tributed by Ms. Rungano Karimanzira, Direc-tor, Projects and Technology Transfer, Minis-try of Higher and Tertiary Education, Science and Technology Development of Zimbabwe during the Concluding Session to the work-shop participants and all those who were in-volved in the organization of this excellent initiative. The Workshop concluded with the participants thanking and greatly applauding the efforts made by the Ministry of Higher and Tertiary Education, Science and Technology Development; the Ministry of Mines and Min-ing Development of the Republic of Zimba-bwe; and the NAM S&T Centre in organizing such a wonderful and useful Workshop. The local organizers were also thanked for holding this highly successful event and for excellent hospitality and arrangements made for the delegates. It was unanimously hoped that more similar events will be held in future. 10. The organizers arranged a NAM S&T Fa-miliarization Tour for the foreign delegates who visited the Diamond Training Centre located at Haydon Estates, Mt Hampden at an hour’s drive from Harare. Mr. Lovemore Kurotwi, Chairman, Zimbabwe Diamond Technology Centre made a presentation on the Centre and its future plans, and the delegates saw the existing diamond cutting and polish-ing facilities as well as the new buildings com-plex of the Centre under construction. ########################HARARE RESOLUTIONS ON MINERALS PROCESSING AND BENEFICIATION

WHILE EXPRESSING GRATITUDE to His Excellency the President of the Republic of Zimbabwe, Robert G. Mugabe, for presiding over the official opening ceremony of the 3rd International Workshop on ‘Minerals Pro-

cessing and Beneficiation’ on the 11th Sep-tember 2014, during which he appreciated the Centre for Science and Technology of the Non-aligned and Other Developing Coun-tries (NAM S&T Centre) as a key thrust and a platform for advancing the developmental im-peratives of the NAM and Other Developing Countries through cooperation in innovation, trade, beneficiation and value addition of their mineral endowment, and offered to host the proposed Non-aligned Movement Science and Technology Centre of Excellence for Mineral Processing and Beneficiation; NOTING WITH CONCERN the array of ini-tiatives from/by developed countries aimed at securing unfettered access to raw minerals from developing countries while discouraging the same developing countries’ efforts for ben-eficiation and value addition; NOTING WITH APPRECIATION the central role and guidance rendered by the Republic of Zimbabwe through the Ministries of Higher and Tertiary Education, Science and Technol-ogy Development; and Mines and Mining De-velopment jointly with the NAM S&T Centre in organising and hosting the international workshop; FURTHER NOTING the contribution of more than 110 participants from 15 NAM and Other Developing Countries; and the presentation of 22 high quality technical papers; HAVING DELIBERATED on mineral re-source endowment, policies, strategies, regula-tory frameworks, research, innovation as well as technological interventions in support of mineral processing and beneficiation in devel-oping countries; RECOGNISING the challenges faced by NAM and Other Developing Countries in mineral development, processing and beneficiation, in-cluding issues of environmental sustainability, technology transfer, skills and infrastructure development; NOTING that actual mineral wealth can be generated by establishment of designated minerals market places and their commodity exchange mechanisms as enablers of value ad-dition, investment, and strengthening the role of developing countries in international trade of their minerals; WE, THE PARTICIPANTS OF THE WORK-SHOP, representing Afghanistan, Guyana, In-donesia, Iran, Malaysia, Mauritius, Myanmar, Nigeria, South Africa, Sri Lanka, Tanzania, Uganda, Vietnam, Zambia and Zimbabwe unanimously resolve to: (i) Immediately undertake the process of es-tablishing the Centre ofExcellence for Mineral Processing and Beneficiation in Zimbabwe; (ii) Establish a taskforce, as part of the above Centre, for preparing draft policy guidelines

and legal frameworks for designated mineral market places and commodity exchanges with-in developing countries to be presented to Af-rican Union Council of Ministers responsible for minerals within the context of the African Mining Vision and AU agenda 2063 and sub-sequently to the AU Heads of State Summit; as well as the NAM Heads of States Summit; (iii) Establish new research & development institutes and strengthen the existing ones for capacity building and mobilise adequate fund-ing for mineral processing and beneficiation in NAM and Other Developing Countries; (iv) Strengthen collaboration among NAM and Other Developing Countries in the setting up and implementation of sustainable and ap-propriate Minerals Development, Processing and Beneficiation Policies including regulatory frameworks; (v) Promote value addition of mineral re-sources and resource-based industrialization through the adoption of sustainable and time bound projects and programmes; (vi) Encourage public social private partner-ships (PSPP) for the development and com-mercialisation of new and emerging technolo-gies and ensuring the role of entrepreneurs and youth ventures; (vii) Promote strategic Human Resource De-velopment in mineral processing and benefici-ation and encourage information exchange of scientists and technologists among NAM and Other Developing Countries; (viii) Facilitate access to high-tech research infrastructure, and international collaboration among NAM and Other Developing Countries and promote localised uptake of innovative technologies; (ix) Strongly recommend that Governments of Developing Countries refrain from engaging foreign Non-state actors including Non-Gov-ernment Organisations in the governance of their mineral resources. It was proposed by the delegate of Uganda to host the next inter-national workshop on this theme sometime in 2016 jointly with the NAM S&T Centre, sub-ject to the availability of funds and necessary government approvals. The participants of the workshop expressed gratitude to them for this kind gesture.

THUS, RESOLVED IN HARARE, REPUBLIC OF ZIMBABWE ON THIS DAY, 13th SEP-TEMBER 2014.

NAM Report on the 3rd International workshop on mineral processing and beneficiation

from page 7


Following appropriate con-sultations in Zimbabwe and on the African continent the

government is working on the es-tablishment of the Pan African Minerals University of Science and Technology (PAMUST). This is borne out of the realization that the African mineral industry has evolved largely as a producer for foreign export markets. Despite its enormous mineral resources Sub Sahara Africa (SSA) has not been able to adequately harness its endowments for its sustainable development and this has been attributed to lack of skills, knowl-edge, technology, infrastructure for innovation and entrepreneur-ship. African countries thus need to embark on the value addition of their minerals in order to boost the development of their economies. The world is changing at a rapid pace, driven largely by develop-ments in science and technology. It has become evident that countries that are scientifically and techno-logically advanced become strong competitors on global markets, therefore generate income, higher wages and wealth. To achieve that, there is need to build world-class Research & Development institu-tions in the minerals sector with linkages to the fabrication sector.In January 2005 at the 4th Ordinary Session of the African Union As-sembly in Abuja the African Heads of State and Government agreed to establish 4 AISTs one each in Western, Eastern, Northern and Southern Africa. The AISTs were to be run by the Nelson Mandela Institution supported by the World Bank among other development partners. The AISTs are tasked to train and develop the next gener-ation of African scientists, engi-neers and technologists, who will impact on the continent’s devel-

opment through the application of science, engineering and technolo-gy. To date, three AISTs have been established namely; in West Africa, the African University of Science and Technology (AUST) in Abuja Nigeria which focuses on Energy and Petrochemical Engineering. The second one was established in Eastern Africa, Arusha, Tanzania, the Nelson Mandela African In-stitute of Science and Technology (NM AIST) which focuses on Life Sciences and Bio-Engineering. The third one was established in North-ern Africa, Ougadougou (Burkina Faso), the International Institute for Water and Environmental Engi-neering (2iE) which focuses on Wa-ter Engineering and Environment. Zimbabwe won the bid to establish the fourth institute, which would be a post-graduate Pan-African Minerals University of Science and Technology (PAMUST) as a centre of excellence in Southern Africa. The centre would be dedicated to the teaching and training of high calibre mineral professionals in mineral beneficiation and value addition for the African continent. PAMUST would also be offering ancillary courses and research in geology, mining and extractive metallurgy as necessary precursors to mineral value addition. More specifically, the following five (5)

programmes would be offered: Geosciences; Mining Engineer-ing; Extractive Metallurgy (ben-eficiation); Materials Science and Engineering for Mineral Value Addition; and Minerals Business Studies.PAMUST will be established pri-marily as a state post-graduate university offering Mastersdegree courses and providing research at PhD and post-doctorate levels. It will be a pan African institution to serve a comprehensive array of needs in the mining industry for the whole continent. Its mission would be to produce a critical mass of graduates who will positively-impact on the continent’s develop-ment and provide leadership in ac-ademia, industry and government for the African mining industry.For the financing of PAMUST, resources are going to be pooled from the joint efforts of African Governments, the Government of Zimbabwe, the Nelson Mande-la Institute, the World Bank and other partners. PAMUST is ear-marked to commence operations using existing infrastructure and facilities at SIRDC. Addition-al facilities and support would be sourced on a need basis from local state universities and colleges.

Pan African Minerals University of Science and Technology (PAMUST)


Copper deposits in Zimba-bwe are found in the Daw-eras Group of the Lomagun-

di Basin in the north-western part of the country. Copper from this area has been mined at Mhangura, Shamrocke and Alaska, which are now dormant. Similar deposits are found in the south-eastern part of the country in the Umkondo Basin, where mining has occurred at Um-kondo mine. The potential of this area has not been thoroughly as-sessed. Significant copper deposits known outside these two environments are the poly-metallic deposits at Cop-per Queen and Copper King (Sanyati). The combined copper oxide/sulphide reserves and resources are 7.6 million tonnes. A considerable amount of copper has also been produced from vein-type deposits at Inyathi. The exploitation of the PGMs in the Great Dyke is also accompanied by significant of Copper as a bye-product. Typically a post smelter matte from the PGM producers contain 31% Copper. Thus current copper production is in the form of by-products from some gold, nickel and PGM mines. Over 70 deposits are known to have produced copper, either as the primary or secondary product. This sug-gests that although currently there is not much going on in the Zimbabwe copper sector, the potential cannot be under-estimated.Copper is a chemical element with the symbol Cu (from

Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; a freshly exposed sur-face has a reddish-orange color. It is used as a conductor of heat and electricity, a building material, and a constit-uent of various metal alloys.Copper tarnishes when exposed to sulfides, which react with it to form various copper sulfidessuchchalcopyrite and chalcocite. It also exists as the copper carbonates azurite and malachite, and the copper(I) oxide mineral cuprite. Most copper is mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits that contain 0.4 to 1.0% copper. Copper can also be re-covered through the In-situ leach process. The amount of copper in use is increasing and the quantity available is barely sufficient to allow all countries to reach developed world levels of usage. The concentration of copper in ores averages only 0.6%, and most commercial ores are sulfides, especially chalco-pyrite (CuFeS2) and to a lesser extent chalcocite (Cu2S). These minerals are concentrated from crushed ores to the level of 10–15% copper by froth flotation or bioleaching. Heating this material with silica in flash smelting removes much of the iron as slag. The process exploits the greater ease of converting iron sulfides into its oxides, which in turn react with the silica to form the silicate slag, which floats on top of the heated mass. The resulting copper matte consisting of Cu2S is then roasted to convert all sulfides into oxides: 2 Cu2S + 3 O2 → 2 Cu2O + 2 SO2The cuprous oxide is converted to blister copper upon heating:2 Cu2O → 4 Cu + O2Like aluminium, copper is 100% recyclable without any loss of quality, regardless of whether it is in a raw state or contained in a manufactured product. In volume, copper is the third most recycled metal after iron and alumin-ium. It is estimated that 80% of the copper ever mined

Copper

Mineral Beneficiation & Value Addition 11Mineral Beneficiation & Value Addition 11

is still in use today. The process of recycling copper is roughly the same as is used to extract copper but requires fewer steps. High purity scrap copper is melted in a fur-nace and then reduced and cast into billets and ingots; lower purity scrap is refined by electroplating in a bath of sulfuric acid. Numerous copper alloys exist, many with important uses. Brass is an alloy of copper and zinc. Bronze usu-ally refers to copper-tin alloys, but can refer to any alloy of copper such as aluminium bronze. Copper is one of the most important constituents of carat silver and gold alloys, and carat solders are used in the jewelry industry, modifying the color, hardness and melting point of the resulting alloys. The alloy of copper and nickel, called cupronickel, is used in low-denomination coins, often for the outer cladding. Alloys of copper with aluminium (about 7%) have a pleasant golden color and are used in decorations. Some lead-free solders consist of tin alloyed with a small pro-portion of copper and other metals. The major applications of copper are in electrical wires (60%), roofing and plumbing (20%) and industrial ma-chinery (15%). Copper is mostly used as a pure metal, but when a higher hardness is required it is combined with other elements to make an alloy (5% of total use) such as brass and bronze. A small part of copper supply is used in production of compounds for nutritional supple-ments and fungicides in agriculture.Machining of copper is possible, although it is usually necessary to use an alloy for intricate parts to get good machinability characteris-tics.Despite competition from other materials, copper re-mains the preferred electrical conductor in nearly all categories of electrical wiring with the major exception being overhead electric power transmission where alu-minium is often preferred. Copper wire is used in pow-er generation, power transmission, power distribution, telecommunications, electronics circuitry, and countless types of electrical equipment.Electrical wiring is the most

important market for the copper industry. This includes building wire, communications cable, power distribution cable, appliance wire, automotive wire and cable, and magnet wire. Roughly half of all copper mined is used to manufacture electrical wire and cable conductors. Many electrical devices rely on copper wiring because of its multitude of inherent beneficial properties, such as its high electrical conductivity, tensile strength, ductility, creep (deformation) resistance, corrosion resistance, low thermal expansion, high thermal conductivity, soldera-bility, and ease of installation.Integrated circuits and printed circuit boards increasingly feature copper in place of aluminium because of its supe-rior electrical conductivity; heat sinks and heat exchang-ers use copper as a result of its superior heat dissipation capacity to aluminium. Electromagnets, vacuum tubes, cathode ray tubes, and magnetrons in microwave ovens use copper, as do wave guides for microwave radiation. Copper’s greater conductivity versus other metals en-hances the electrical energy efficiency of motors. This is important because motors and motor-driven systems ac-count for 43%-46% of all global electricity consumption and 69% of all electricity used by industry. Increasing the mass and cross section of copper in a coil increases the electrical energy efficiency of the motor. Copper motor rotors, a new technology designed for motor applications where energy savings are prime design objectives, are enabling general-purpose induction motors to meet and exceed premium efficiency standards. Copper oxide and carbonate is used in glassmaking and in ceramic glazes to impart green and brown colors.Cop-per is the principal alloying metal in some sterling silver and gold alloys. It may also be used on its own, or as a constituent of brass, bronze, gilding metal and many oth-er base metal alloys.


Zimbabwe is a modest pro-ducer of Manganese with an average export of 100 metric

tonnes of manganese ore per year. However, the available manganese was used in the steel industry at ZISCO and will certainly be im-portant for ESSAR’s New Zimsteel when it comes into operations.Nearly 90 percent of the manga-nese consumed in the world is used in the production of steel, ei-ther as an alloying element or as a processing agent. Consumption of manganese in this industry is de-pendent not only on the level of steel production, but also on the mix of steel grades produced and processing technologies used. This article discusses the function of manganese in both steel and steel-making, and assesses the effects of product and processing trends on the pattern of manganese use in the steel industry. Manganese is second only to car-bon in importance as an alloying element in steel. Through its influ-ence on steel chemistry and micro-structure, manganese influences an assortment of physical and me-chanical properties. Manganese provides sulfur control, enhanc-es hardenability, wear resistance, and solid solution strengthening, and retards recrystallization. The

amount of manganese used as an alloying element depends on the specific property requirements of the particular steel product. Some grades make greater use of it than do others. In nearly all grades of steel, sul-fur is an unwelcome impurity. It is a tramp element that is picked up from the coking coal, fuel oils, and ferrous scrap used in the pro-duction of iron and steel. Iron and sulfur form compounds (FeS) at the grain boundaries within steel, causing a detrimental condition known as “hot shortness.” Prob-lems arise because FeS has very little structural integrity, being either liquid or extremely plastic at the temperatures encountered during manyfinishing (hot work-ing) operations. The presence of this strengthless phase as a film along the network of grain bound-aries severely weakens steel at high temperatures and causes cracking during fabricating operations. Fur-thermore, in ferritic grades, FeS causes problems with low-tem-perature mechanical properties. To minimize these effects, the sul-fur content is typically held below 0.05 percent by weight. Manganese is added to react with the remain-ing sulfur, which would otherwise combine with iron. The globular

MnS precipitates formed upon the addition of manganese are solid at typical hot working temperatures and are structurally amenable to hot forming operations. Althoughit is not a remedy for all sulfur-relat-ed problems, manganese generally improves both the high- and low-temperature properties of steel. Heat treatment is the most potent method for optimizing the strength and duc-tility of steel. The cooling rate re-quired to form a given mar-tensite profile during the heat treatment quench is a very import-ant parame-ter, known as “hardenabi l -ity,” of steel. Additions of the common alloying elements, namely molybdenum, man-ganese, chromium, silicon, and nickel, facilitate the formation of martensite, thereby reducing the cooling rate requirement and in-creasing the hardenability of steel.

Manganese


Manganese is a very cost-effective hardenability agent and conse-quently is one of the most vital al-loying elements for influencing the response of steel to heat treatment.

An allied effect of some al-loying elements con-

cerns their influence on the shape and

distribution of iron carbides in steel. Weld embrittle-ment can occur if the iron carbides form a contin-uous film at the grain boundaries during the ther-

mal excursion. Manganese tends

to enhance weld-ability of steel by in-

hibiting the develop-ment of such film.

Manganese, like nick-el, lowers the austen-

ite-to-ferrite transforma-tion temperature of steel and

is termed an austenite stabilizer. High-carbon steels that remain austenitic at room temperature can be produced by adding man-ganese to levels greater than 10 percent by weight. Austenitic steels as a class are attractive because their strength increases marked-

ly as they are deformed and they have excellent resistance to frac-turing under impact conditions, two properties important for wear resistance. The austenitic manga-nese grades, called Hadfield steels, display good abrasion and impact resistance and serve in construc-tion, mining, quarrying, oil-well drilling, steelmaking, cement and clay manufacturing, railroading, dredging, and lumbering appli-cations. Other austenitic grades(-containing 15 to 25 percent man-ganese) have been developed for their nonmagnetic properties and high toughness. These high-man-ganese austenitic steels are suit-able for structural uses in strong magnetic fields and at cryogenic temperatures and may replace the stainless steels commonly used in these applications. Steel generally becomes stron-ger when an alloying element is dissolved in the iron phases. This effect is known as “solid solution strengthening.” It is a very import-ant means of strengthening ferritic steels, which cannot be strength-ened by heat treatment. Alloying elements vary markedly in their potency as solid solution strength-eners. In ferritic steels the order of decreasing effectiveness appears to be: silicon, manganese, nickel,

molybdenum, vanadium, tung-sten, and chromium. While sili-con is highest on this list, it is not used extensively because of an ac-companying loss of ductility. Thus, manganese has great utility as a solid solution strengthener. When steel is deformed or heavily worked, its microstructure is al-tered in a way that is detrimental to the properties of steel. To alleviate problems, steel in this condition is usually annealed, whereupon the microstructure is recrystallized. Manganese slows the rate of re-crystallization considerably. This is not a desirable effect and can have negative impacts on the produc-tivity of various steel-treating pro-cesses, such as continuous anneal-ing operations. Steel is produced in a myriad of compositions, and the relative popularity of each grade changes as consumer demands shift. Trends in manganese use vary among the four broad cate-gories of steel: carbon, full alloy, high-strength low-alloy (HSLA), and stainless. All four classes con-tain manganese, but in differing proportions.

Manganese

Rare earths


Abundance of Rare earths

The rare earth elements are Lanthanum (La), cerium (Ce), Praseodym-ium (Pr) neodymium (Nd), Samarium (Sm), Europium (Eu), Terbium (Tb), Gadolinium (Gd), Dysprosium (Dy), Holmium (Ho), Lutetium (Lu), Promethium (Pm), Thulium (Tm) and Ytterbium (Yb). Often Yttrium (Y) and Scandium (Sc) are also thrown into the rare earths basket. Before discussing the value addition of rare-earths, which are also often referred to as lanthanides, it is important to get a feel of their relative abundance in the earth’s crust. Oxygen, silicon and aluminium are conspicuously the most abundant elements. More notably the rare earths are not as rare after all! In fact, the platinum group metals (for which Zimbabwe has the second known largest deposit in the world) and gold, which are collectively known as the precious, are actually the rarest elements. So, why are the lantha-nides called the “rare earth” metals? This is probably due to the fact that although the combined global quantum is not miniscule, the dis-covered minable concentrations of rare earths are much less common than for most ores. Mineral Processing of Rare-earthsThe two main ore sources of rare earths are bastnäsite and monazite. Most of the global supply of rare earths comes from the bastnäsite ores of China. The run-of mine (ROM) bastnäsite ores contain about 7% total rare earth oxides (REO). The ore is typically passed through the conventional comminution circuit of crushing and grinding before its conditioned and subjected to flotation. The resultant floatation concen-trate contains about 60% REO after being dried. The concentrate is then acid leached usually with hydrochloric acid, to yield a concentrate with approximately 70% REO before being subject-ed to an oxidising roast, which results in a higher grade concentrate with about 85% REO. The concentrate is further subjected to Redox separation processes and a judicious combination of precipitation and solvent extraction to yield the individual rare earth oxides. It is possible to produce metallic rare earth elements from their individual oxides

through converting the oxides to their respective chlorides followed by electrolysis or metallothermic reduction. Rare-earth usesSome of the major applications include permanent magnets (e.g. Nd-Fe-B), fluorescent lamps, batteries, fibre optics .The increased usage of metallic rare earths in magnets and batteries

are driven by the global efforts to curb CO2 emissions. The rare earth permanent magnets, which are mostly based on Nd, are particularly attractive due to their high energy density, enhanced thermal stability and improved pricing. Neodymium iron boron (NdFeB) magnets are considered to be the strongest permanent magnets available commer-cially; capable of holding more than 1300 times their own weight. In 2008, approximately 63 600 tonnes of sintered NdFeB magnets were produced, in the same year, a further 5000 tonnes of bonded NdFeB magnets were produced mostly in China, Japan and the EU. The de-mand for NdFeB magnets is fuelled mostly by hybrid vehicles, elec-tronic application (iPods, walkmans), motors, e.g. for wind turbines. It is projected that by 2020, the neodymium magnet market could exceed US$10 billion. Growth of the NiMH battery market, which utilises mostly lanthanum, will also be fuelled by the automotive industry. NiMH batteries are currently being used in one of the flagship hybrid vehicles-the Toyo-ta Prius, which uses approximately 12 kg of lanthanum. Projections are that this will rise to approximately 20kg. The growth of the NiMH batteries market could however be potentially curtailed by parallel de-velopments on the use of Li-ion batteries especially in hybrid vehicles. Li-ion batteries have higher energy and power densities. It is common knowledge that Zimbabwe also has lithium deposits in Bikita, which could potentially be used in the production of Lithium ion batteries.Another interesting rare earth market that could grow beyond projec-tions is the phosphor market, which relies on rare earth compounds, mostly oxides. Other than the conventional plasma screen usage, the recent development of more energy efficient compact fluorescent lamps could result in a significant uptake of rare earth based phosphors.It is clear that China dominates the global supply and also demand for rare earths. The skewed global production of rare-earths is a serious concern for global markets, especially in light of their broad uses. An opportunity exists for countries like Zimbabwe to really explore the ex-istence of rare earths in the country, especially considering that some of the geological-mineralogical markers for the occurrence of rare-earths have been observed Zimbabwe.


In Zimbabwe tin has been produced at Kamativi for many years but was decommissioned in 1992, when tin prices plummeted. Recent geological surveys has revealed that there are millions of tonnes of

untapped tin ore reserves at the old Mine. Mining operations could be revived profitably with a lot of downstream industries considering the various uses of tin. In fact Ministry of Mines and Mining Development, through ZMDC, is exploring the options of opening the mine with a view to exploit tin and the other associated minerals such as tungsten, tantalite, niobium (or columbite), beryllium, lithium and mica.Tin is obtained chiefly from the mineral cassiterite, where it occurs as tin dioxide, SnO2. This silvery, malleable other metal is not easily ox-idized in air and is used to coat other metals to prevent corrosion. In modern times tin is used in many alloys, most notably tin/lead soft sol-ders, typically containing 60% or more of tin. Another large application for tin is corrosion-resistant tin plating of steel. Because of its low toxic-ity, tin-plated metal is also used for food packaging, giving the name to tin cans, which are made mostly of steel.Commercial grades of tin (99.8%) resist transformation because of the inhibiting effect of the small amounts of bismuth, antimony, lead and silver present as impurities. Alloying elements such as copper, antimo-ny, bismuth, cadmium and silver increase its hardness. Tin tends rather easily to form hard, brittle intermetallic phases, which are often unde-sirable. Tin(II) chloride (also known as stannous chloride) is the most import-ant tin halide in a commercial sense. Tin can form many oxides, sul-fides, and other chalcogenide derivatives. The dioxide SnO2 (cassiterite) forms when tin is heated in the presence of air. SnO2 is amphoteric, which means that it dissolves in both acidic and basic solutions. Tin is the 49th most abundant element in the Earth’s crust, representing 2 ppm (parts per million) compared with 75 ppm for zinc, 50 ppm for copper, and 14 ppm for lead. Tin does not occur as the native element but must be extracted from various ores. Cassiterite (SnO2) is the only commercially important source of tin.Because of the higher specific gravity of tin dioxide, about 80% of mined tin is from secondary deposits found downstream from the primary lodes. Tin is often recovered from granules washed downstream in the past and deposited in valleys or under sea. The most economical ways of mining tin are through dredging, hydraulic methods or open cast min-ing. Most of the world’s tin is produced from placer deposits, which may contain as little as 0.015% tin. Tin is produced by carbothermic reduc-tion of the oxide ore with carbon or coke. Both reverberatory furnace and electric furnace can be used. About half of tin produced is used in solder. The rest is divided between tin plating, tin chemicals, brass and bronze, and niche uses. Tin has long been used as a solder in the form of an alloy with lead, tin accounting for 5 to 70% w/w. Tin forms a eutectic mixture with lead containing 63% tin and 37% lead. Such solders are primarily used for solders for joining pipes or electric circuits. Tin bonds readily to iron and is used for coating lead or zinc and steel to prevent corrosion. Tin-plated steel containers are widely used for food preservation, and this forms a large part of the market for metallic tin. The tin whis-tle is so called because it was first mass-produced in tin-plated steel. Tin in combination with other elements forms a wide variety of useful alloys. Tin is most commonly alloyed with copper. Pewter is 85–99% tin; Bearing metal has a high percentage of tin as well. Bronze is mostly copper (12% tin), while addition of phosphorus gives phosphor bronze. Bell metal is also a copper-tin alloy, containing 22% tin.

The niobium-tin compound Nb3Sn is commercially used as wires for superconducting magnets, due to the material’s high critical temperature (18 K) and critical magnetic field (25 T). A superconducting magnet weighing as little as two kilograms is capable of producing magnetic fields comparable to a convention-al electromagnet weighing tons. The addition of a few percent of tin is commonly used in zirconium alloys for the cladding of nuclear fuel. Most metal pipes in a pipe organ are made of varying amounts of a tin/

lead alloy, with 50%/50% being the most common. The amount of tin in the pipe defines the pipe’s tone, since tin is the most tonally resonant of all metals. When a tin/lead alloy cools, the lead cools slightly faster and produces a mottled or spotted effect. This metal alloy is referred to as spotted metal. Major advantages of using tin for pipes include its appearance, its workability, and resistance to corrosion. Window glass is most often made by floating molten glass on top of molten tin (creating float glass) in order to produce a flat surface. This is called the “Pilkington process”. Tin is also used as a negative electrode in advanced Li-ion batteries. Its application is somewhat limited by the fact that some tin surfaces catalyze decomposition of carbonate-based electrolytes used in Li-ion batteries. Tin(II) fluoride is added to some dental care products as stannous fluoride (SnF2). Tin(II) fluoride can be mixed with calcium abrasives while the more common sodium flu-oride gradually becomes biologically inactive combined with calcium compounds. It has also been shown to be more effective than sodium fluoride in controlling gingivitis. The major commercial application of organotin compounds is in the stabilization of PVC plastics. In the absence of such stabilizers, PVC would otherwise rapidly degrade under heat, light, and atmospheric ox-ygen, to give discolored, brittle products. Tin scavenges labile chloride ions (Cl-), which would otherwise initiate loss of HCl from the plastic material. Typical tin compounds are carboxylic acid derivatives of dibu-tyltin dichloride, such as the dilaurate. Tin forms several inter-metallic phases with Lithium metal and it makes it a potentially attractive material. Large volumetric expansion of tin upon alloying with Lithium and instability of the Tin-organic electro-lyte interface at low electrochemical potentials are the greatest challenges

in employing it in com-

mercial cells.

Tin


Gold has been revered in almost all human cul-tures for as long as civilizations have been able to admire – and use – this precious metal’s

unique properties. Goldis extremely malleable, con-ducts electricity, doesn’t tarnish, alloys well with other metals and is easy to work into wires or sheets. Not to mention, gold is unrivaled in its natural brilliant luster and glossy shine. Because of these unique properties, gold makes its ways into almost every sphere of mod-ern life in some way, shape or form.Investment bars: Gold can be kept as a gold bar and used for investment purposes. Most central banks and other official bodies hold gold as part of their external resources. This is because gold is such a secure asset. It is an asset that can actually be seen and touched and it is indestructible. The beauty of gold is that it is uni-versal and is often used in political or economic crises because gold is valuable throughout the world. Gold bars are not just held by large companies and central banks but are also available to the private collector as well. Because gold is so rare and highly valued, this precious metal makes a natural currency, and has for at least 6,000 years. In an uncertain economy, gold has emerged as a possible financial staple. One of the most common ways to hold or invest in gold is in gold coins, gold bars, also gold bullion. Jewelry: Gold alloys are used in the jewelry industry in the form of sheet, wire, granules, solders, and discs. Gold alloys in the jewelry industry are a common use of gold. Gold is used because it is highly malleable and easy to manipulate. This is why gold is the prime choice for jewelry because it’s versatility makes it per-fect to create the most exquisite pieces. About 78% of gold consumed each year is made into jewelry. Jewelry is the most common way gold reaches consumers, and has been a primary use for the metal in various cul-tures. Because of its beautiful and durable properties, gold jewelry is an adornment that is both ethereal and revered. Especially in India, adorning the body with gold is a way to attract wealth and blessings. There are so many different types of jewelry. Gold is used in the manufacture of many different types of jewelry, including watches, rings, bracelets, anklets, eyebrow rings, nose rings. The beauty of gold is that it doesn’t rust, doesn’t corrode, doesn’t turn your skin green, and it looks absolutely beautiful. Catalysts: A catalyst is a substance that accelerates the

rate of chemical reaction without being consumed in the reaction. Gold alloy catalysts are used in the pro-duction of paints and glue. Gold catalysts also have the potential to remove nitrogen oxide from diesel engine exhausts. Gold catalysts are now also being tri-alled to help improve the air quality in underground

mining environments. An interesting and new use of gold catalysts is that they are now being used to re-move odours from public toilets in Japan. Reflective ability: The reflective ability of gold makes it the ideal for substance for many different uses. Space shuttles are covered with a thin sheet of gold to help improve the craft’s reflective ability. As-tronauts are provided with gold sunglasses to protect their eyes from direct sunlight. Cockpit windows have a thin film of gold over them to reflect the harmful effects of the sun’s rays. Gold has been used over the years to adorn buildings because its resistance to cor-rosion will outlast paint every time. In the aerospace industry where reliable and effective technologies are key to survival, gold plays an essential role. Gold is used to lubricate mechanical parts, conduct electricity and coat the insides of space vehicles to protect peo-ple inside from infrared radiation and heat. It is also used in modern buildings to cover windows because it helps retain heat in winter and reflects it in summer. It is thought to cut heating and cooling costs by 40%. One ounce of gold will cover 1000 sq. feet of glass. Electronics: The merits of gold are unparalleled. Gold is malleable, ductile, deflectable, it is resistant to corrosion, and is a great conductor of electricity. We come into contact with gold every single day and probably don’t even realise it. In the morning when your alarm clock goes off, it’s got gold in it. Also your microwave, your washing machine, your television, calculators and mobile phones. Some DVDS and re-cordable CD-Roms also have gold within their con-


struction. It is used in automotive, electronics, mis-siles, spacecraft. In the electronics industry gold is an irreplaceable substance. Gold is a highly efficient conductor that is able to carry tiny electrical charges, and because of this property a small amount is found in almost all electronic devices, including cell phones, televisions, GPS units and more. Because gold is such an efficient conductor of electrical charges, it is also often found in desktop and laptop computers to trans-fer information quickly.Automotives: Even cars now use gold in their elec-trics. Ignition control electrics, anti-lock braking systems, electronic fuel injectors, and even the crash sensors for air bags have gold connectors. The malle-ability and ductility of gold as well as its conductive properties make it a very useful and reliable metal.

Medicine: Gold has been used for medicinal purpos-es for thousands of years. It has now become obvious to our medical population that there are many me-dicinal uses for gold. Gold injections are used to help alleviate the pain of arthritis. Inner ear implants are now also made out of gold. Gold’s resistance to bac-terial infection make it perfect for implants. Wires to pacemakers are also made out of gold. Gold dust in the form of tablets is said to relieve you of fatigue and depression. It has now also become the focus for new trials in the treatment of cancer. One of the latest uses of gold is drug-delivery microchips that are injected or swallowed into the body. These chips contain drug-filled reservoirs that are covered with thin gold mem-branes. The drugs are then released into the system at

the required time. Small amounts of gold isotopes are used in certain radiation treatments and diagnosis.Dentistry:Gold’s malleability and resistance to corro-sion make it ideal for dentistry and is a very popular substance. The malleability of gold makes it perfect to create false teeth, caps or crowns. As far back as the 7th century the Etruscans used gold to secure false teeth into their mouths to replace the ones that were lost. Gold makes for the best fillings, crowns, bridges and orthodontic appliances because the metal is chemical-ly inert, easy to insert and non-allergenic. Gold has been used in dentistry since 700 B.C. and will proba-bly continue to be the best option for replacing broken or missing teeth.Religious artifacts: Religious artefacts have for thou-sands of years been made from gold. The most famous piece of gold is probably the face mask of the boy king of Egypt, Tutankhamen. Gold leaf is used in many paintings and is also used to decorate glass and fine china. Gold plating: Trophies are a popular gold-plated item but it is interesting to note that the Soccer World Cup trophy is actually 36 cm of solid gold. As a high-ly esteemed precious metal, gold makes a natural appearance in crowns, awards and religious statues. Because of its unparalleled beautiful qualities and rar-ity, gold is one of the highest status symbols. In every-thing from Academy Awards to Olympic medals, gold is recognized for its admirable qualities and it holds a permanent place of value in humanity’s eyes. Many of the things we use around the house can be gold plated: Pens, Watches, Trophies, Bathroom fittings, Spectacle frames.Conclusion: The uses of gold are numerous. Gold has gone far beyond being just an ornamental element. Its uses are becoming essential to our modern environ-ment. So without gold we would be leading very dif-ferent lives. A life less technologically advanced and definitely a world less beautiful. There are many great lessons for us in value addition to gold.


Cobalt (chemical symbol-Co ) is a prime example of a “strategic mineral.” Cobalt

alloys are important to a number of industries, especially aerospace and defense. Cobalt is a hard, brit-tle, metallic element found in asso-ciation with nickel, silver, lead, cop-per, and iron ores and resembling nickel and iron in appearance. Its most common use is in alloys to which it imparts qualities such as heat resistance, high strength, wear resistance, and superior magne-tism. Major end-products include jet engine parts, permanent mag-nets, cutting tools, and pigments.In Zimbabwe cobalt is produced as a by-product of nickel and plat-inum ores. At independence in 1980, there were three Nickel pri-mary producers in the country,

with a combined output probably approaching 15,000 tonnes/year Nickel metal. Anglo American operated the Trojan and Madzi-va mines in the Bindura/Shamva area and the new Epoch mine in Filabusi. The company operated a smelter/refinery at Bindura which treated not only concentrates from its own mines but also from the secondary producers, Johannes-burg Consolidated Investment’s Shangani operation located near Inyati which had an output at about 2,500 tonnes/year contained Nickel. The third major producer was Rio Tinto Zimbabwe with the Empress and Perseverance mines and a central smelter/refinery at Kadoma. Considerable problems

were experienced with the Perse-verance property on account of an unacceptably high arsenic content in the concentrates which adverse-ly affects smelter operations. At present only Trojan Mine is oper-ating for the production of Nickel. The others have either shut down completely or are under care and maintenance. Aside from the above producing mines there is one ma-jor prospect. This is the Hunters Road, in the Midlands, founded by Anglo Amerian, reputed to be the largest and potentially most profitable deposit in the country. The exploitation of the PGMs in the Great Dyke is accompanied by significant yield of Nickel, Cop-per and Cobalt as a bye-products. Typically a post smelter matte from the PGM producers contain

45% Nickel, 31% Copper and 0.5% Cobalt while the combined PGMs constitute only 0.2%. Several methods exist for the sep-aration of cobalt from copper and nickel. They depend on the concen-tration of cobalt and the exact com-position of the used ore. One sepa-ration step involves froth flotation, in which surfactants bind to differ-ent ore components, leading to an enrichment of cobalt ores. Subse-quent roasting converts the ores to the cobalt sulfate, whereas the cop-per and the iron are oxidized to the oxide. The leaching with water ex-tracts the sulfate together with the arsenates. The residues are further leached with sulfuric acid yielding a solution of copper sulfate. Cobalt

can also be leached from the slag of the copper smelter. The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to the metal by the aluminothermic reaction or reduction with carbon in a blast furnace. The copper belt in the Democratic Republic of the Congo and Zam-bia holds64% of the cobalt mined worldwide. The USA and Europe countries do not produce cobalt. Thus, aside from cobalt stockpiles and the recycling of used materials, these countries are completely de-pendent on imports. This gives rise to two kinds of their vulnerability. The first is essentially military in nature: the possible need to wage a war in the absence of foreign sup-plies of cobalt. The second is eco-nomic: the effect on the economy of a disruption in foreign supply with an attendant sudden increase in price. The tight market results from a combination of factors: mil-itary conflict in DRC, expanding industrial economies, and a change in stockpile policy of industrialised countries. Price increases has sig-nificant effects on cobalt demand, precipitating searches for substi-tutes, improved conservation, and increased recycling from scrap. Cobalt is usually employed as an alloy with other metals where it imparts qualities such as heat re-sistance, high strength, wear re-sistance, and superior magnetism to the materials that are formed. Consumption of cobalt is divided among alloys for jet engines and stationary gas turbines, permanent magnets for electrical equipment, machinery, and nonmetallic appli-cations. Cobalt is used in batteries. Lithium cobalt oxide (LiCoO2) is widely used in lithium ion battery cath-

Cobalt



GraphiteThe most discussed allotrope of carbon in Zim-

babwe is diamond. Zimbabweans are rightfully seized with the issue of diamond mining, the

potential revenue and how this can contribute to the economy within the ZIM ASSET frame work.In the process, the other allotrope of carbon, namely graph-ite has perhaps slipped under the radar, never mind that we use graphite pencils in our everyday lives!For completeness, the other allotropes of carbon include amorphous carbon (incorporating coal), graphene, fullerenes and nanotubes;any additional discourse on these ishowever beyondthe scope of this brief treatise. It turns out that Zimbabwe is one of two countries in Africa with developed natural graphite mines, the oth-er country being Madagascar. Somewhat fortuitous-ly, both countries have nearly identical name plate production capacities of around 15 000 tonnes/year, although in recent years production in both coun-tries has sharply declined to almost a third of this. In 1987, Zimbabwe accounted for about 2% of the world graphite production. Natural graphite occurs as flakes, veins or as amorphous masses.The graphite obtaining in Zimbabwe, which is produced at Lynx Mine in Karoi,is the flake type; this generally fetches a premium on the international market, which could be as much as US$1500/tonne depending on the size of the flakes and carbon content. In 2011/2012, the price for +80 mesh graphite with 94-97% carbon peaked at over U$2500/tonne. The mineral processing of graphite is reasonably straightforward. The run of mine (ROM) ore with about 5-30% graphite is typically sent through a jaw

crusher, a cone crusher and a rod mill before the graphite is floated in rougher flotation cells to yield a rougher graphite concentrate. In some instances, air classification is used to pre-concentrate the graph-ite prior to rougher flotation. The rougher flotation graphite concentrate is further milled in a rod mill before being sent for a final cleaner flotation, which yields a final concentrate with 75 to 97% graphite. Although graphite is easily floatable on account of its hydrophobic nature, it is common to use reagents such as kerosene (to coat the graphite) and pine oil (a froth stabiliser) to enhance the graphite floatation behaviour.Higher grades of 90% and above are more difficult to produce, and often require additional hy-drometallurgical processing to rid the graphite of im-purities such as quartz, feldspar, mica, etc. The value addition of graphite in Zimbabwe pretty much ends with the +75% graphite concentrate.To understand the potential scope for further value addition of flake graphite, it is instructive to look at some of the applications of flake graphite.The main areas of natural graphite application are refractories such as magnesia graphiteand alumina graphite. Both these refractories require a minimum carbon con-tent of 85%. The graphite produced at Lynx Mine has about 80-95% carbon. Crucibles and mould washes are other additional applications of graphite in the metal casting industry. It is hoped that Essar become-soperational; the demand for refractories in Zimba-bwe’s metals industry will start to steadily grow. The demand for natural flake graphite in brake and clutch linings can be expected to also increase as new


Graphiteautomobile production continues to increase and more replacement parts are required for the grow-ing number of vehicles. These applications howev-er require a minimum carbon content of 98%C.This requires the additional upgrading of the Zimbabwe graphite before tapping into this market. Still on auto-motive applications of graphite, the advent of hybrid and electric vehicles is expected to bring increased demand for high-purity graphite in fuel cell and bat-tery applications. Optimistic predictionsare that the demand for high quality, high carbon graphite could increase to more than 100,000 metric tonnes per year for fuel cell and battery applications alone, and that the global demand for graphite used in batteries may exceed 25,000 t/yr in the next couple of years. This de-mand is expected to bespread between the two main consuming sectors-alkalinebatteries and lithium-ion batteries. Both synthetic and natural graphite can be used in these batteries.In alkaline batteries, graphite is the conductive material in the cathode. Until recently, synthetic graphite was dominantly used in these bat-teries. But with the advent of new purificationtech-niques and more efficient processing methods, it has-become possible to improve the conductivity of most naturalgraphite to the point where it can be used in batteries. The decision on whether to use synthetic or natural graphite is generally a balancing act between price and performance considerations. The growth of the lithium-ion battery market could have a more dra-matic effect on the graphite market as the demand rises for mobileenergy storage systems.Fuel cells con-vert hydrogen into electricity via an electrochemical

reaction. The hydrogen molecules break down into protons and electrons at the cell’s anode. Protons are thenconducted through the electrode and the elec-trons travel through an external circuit and generate electricity. Graphite,as cathode material, forms a cru-cial part of fuel cell technology. Projections are that the consumption of graphite in fuelcell electrodes could reach 80,000 t/yr soon.Canada, Germany, Ja-pan, and the United States, and now more recently South Africa are aggressively promoting fuel cell de-velopment. The cost of fuelcells, however, is still too high for commercial vehicles.For Zimbabwe, the lithium-ion battery and fuel cell applications of graphite must be seen in a much wider context in light of the country’s lithium and platinum deposits, which are key electrode materials in these applications. Any national attempts to add value to graphite with a specific focus on these applications, must be synchronised with similar value addition ac-tivities for lithium and platinum, otherwise there will always be a missing piece in the jigsaw puzzle.It is clear that while Zimbabwe is endowed with flake graphite deposits, much work still need to be done to upgrade our graphite to levels that allow us to tap into the growth market applications of graphite. Even the pencil we use in our everyday lives requires graphite with a minimum carbon content of 95 -97%C, this against our current grades of 80 -95% C. Also, any value addition attempts must be well thought out and holistic.

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Mineral Journal · 2016. 9. 1. · Science and Technology Development and the Ministry of Mines and...

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