The primary source of diamonds are Kimberlites and Lamproites, these occur as pipes and dykes from the earth’s crust. Only a small proportion of Kimberlites and Lamproites are diamondiferous. The Chiadzwa alluvial diamonds are a product of weathering and erosion of the primary source.
The weathered diamondiferous material was transported by fluvial processes and deposited in the shallow basin in Chiadzwa in the Umkondo sedimentary formation aged about 1 billion years old. The diamonds in Chiadzwa were carried from the primary source and deposited in basal conglomerate rock which is a secondary source /environment.
Subsequent weathering and erosion of the conglomerate rock further liberated the diamonds into a tertiary source where they occur in their natural state on slopes, paleo channels, low lying areas, streams and rivers. These diamonds in the tertiary environment are generally called alluvial diamonds.
Alluvial diamonds are relatively easy to mine as only excavation, hauling and processing is involved. There is no need to drill and blast the host rocks to liberate diamonds. In layman’s terms, alluvial diamonds are “the low hanging fruit” in diamond mining due to the simplistic mining and processing methods that can be used to recover them.
Alluvial diamonds were first mined in Marange in 2006 and in 2009. Eight companies were issued with Special Grants to mine diamonds in Marange and in Chimanimani.
History of diamond mining in Zimbabwe
Diamond Production Trends
Up to the time of consolidation of the concessions by Government, the former mining companies were almost entirely mining alluvial deposits as these required less resources to mine compared to the conglomerate deposit. The alluvial deposit was being depleted and by 2014 most of the mining companies had exhausted the rich pockets of rich alluvial deposits which were economically viable to mine. The graph below shows the production trends in diamonds
Zimbabwe Consolidated Diamond Company (Pvt) Ltd (ZCDC) was formed following the March 2015 Government decision to consolidate all diamond mining companies in Zimbabwe to form a wholly owned Government Company.
The Government’s objective was to ensure that there would be transparency, accountability and optimal commercial exploitation and marketing of Zimbabwe’s diamonds
Zimbabwe Consolidated Diamond Company (Pvt) Ltd (ZCDC) was formed with the following mandate.
- To enhance adequate investment in diamond mining beyond alluvial.
- To explore for kimberlitic resources and build bankable mining reserves.
- To enhance contribution to fiscus and community development
- To enable Government to manage more efficiently operations and exploitation of the country’s diamond resources.
- To achieve better accountability and transparency.
Moving towards sustainability
When ZCDC commenced operations in February 2016 it continued from where the former miners left off, processing alluvial deposits from various concessions (Portals). Using modern X ray recovery technology, the company was able to recover diamonds from processed material while looking for new areas to mine. As the operations progressed it became apparent that the rich alluvial deposits had been mined out and the remaining deposits were becoming increasingly uneconomic to mine with high stripping ratios. With the depletion of rich alluvial deposits, the company managed to produce 961,537 carats in 2016.
The Diamond Mining Business Model
Through the implementation of a carefully deliberated and crafted Diamond Mining Business Model (DMBM), the company presented a strategic business plan to its shareholder and subsequently received capital to invest in a sustainable mining model which would usher in conglomerate mining.
ZCDC’s Diamond Mining Business Model (DMBM) was premised on the promotion of organization stability, business growth and mining sustainability.
Stability entailed dealing with all issues that threatened the going concern status of the business which included, legacy debt overhang, legal disputes from consolidation, undercapitalization, depleted alluvial deposits among other issues. It also entailed implementing best practice Systems, Policies and SOPs, capacitating owner mining model, incorporating effective security systems anchored on technology and incorporating business optimization in all business decisions.
Business Growth encompassed investment into current operations to build current and future production capacity and diamond output. It also entailed, investing in intensive evaluation and exploration to promote confidence mining, creating a balance sheet of proven bankable reserves, investment in increasing machine and equipment availability for mining, consolidation of plant efficiencies for diamond recovery and realization of maximum value, bringing all Portals (concessions) into operation and achieving growth in ROM an capacitating downstream process i.e. sorting, cleaning and valuation framework to enhance Diamond Value Management (DVM).
Sustainability entailed mining for the benefit of both current and future generations, promoting diamond mining for posterity. It compelled, expansive evaluation and exploration for sustainable Conglomerate and Kimberlitic mining, feasibility studies on exploration to have turnkey projects for sustainable mining in greenfield concessions and building confidence levels to have bankable diamond reserves and mining plans, investment in new technology in mining, processing and evaluation and creating self-financing capacity for futuristic and sustainable diamond production.
Towards a sustainable mining model
The transition from an alluvial to a conglomerate and kimberlitic based model
In line with the dictates of the DMBM, in the second quarter of 2017, the ZCDC Board approved investment into a 450 tonne per hour conglomerate processing plant to be installed at Portals (A & B). The total investment was $15 million.
As part of Plant design optimization comprehensive metallurgical rock crushability tests were carried out on all mining concessions. The tests are an important part of Diamond Value Management (DVM) as they minimize the damage of diamonds during recovery which affects the value of rough diamonds. The results will also enhance further understanding of the depositional environment and potential source of the diamonds.
Future Mining plans
As inscribed in its DMBM, ZCDC will implement a mining sustainability strategy which is aimed at opening new mines. Two more mines will be opened in 2018 to complement production at Chiadzwa and Chimanimani. Extensive investment has been made in exploration and resource evaluation to discover and validate new diamond discoveries across the country. Work has already begun in various areas with reported diamond discoveries.
Investment towards Kimberlite mining
Investment in exploration and evaluation is key in building resource confidence and generating feasible mining plans to guide mine planning and business optimization which are informed by confirmed resource statements. This minimizes capital at risk and enhances shareholder value.
ZCDC owns ore resources that are mainly in the inferred category which require further evaluation to upgrade to indicated and measured category. At the same time the company needs to explore for new additional ore resources to open new mines and increase production. As such the company has embarked on a structured and intense exploration and evaluation exercise for short term, medium term and long term projects in line with the Diamond Mining Business Model.
ZCDC invested $7.1 million towards exploration and evaluation and has targeted over $2 million in 2018 to create a balance sheet of proven bankable reserves
Exploration is underway across Zimbabwe in search of kimberlite pipes.
ZCDC Mining Sustainability plans