Special Mining Lease No 23 measuring 1,661 hectares is located within the Kwale Prospecting License PL/2018/0119 area of 88km2 and is located approximately 50km south of Mombasa, and 8km inland from the Indian Ocean.
The Project resource comprises two dunes that contain economically viable concentrations of heavy minerals, which are separated by the Mukurumudzi River. These are the Central and South Dunes. A third dune, the North Dune is not currently included in the Project.
Geology & Mineralisation
The Magarini Sands, which host the Kwale deposit, are of aeolian origin deposited as coastal dunes after conditions of intense erosion. The poorly stratified deposits form a belt of low hills running parallel to the coast. Heavy minerals (“HM”), mainly ilmenite, rutile and zircon, are concentrated locally and are abundant in some places. The deposits also contain a clay and silt fraction of 25 to 30%.
The general stratigraphic sequence of the Kwale deposit, as seen below, is composed of brown sand at the surface, followed by orange or reddish sand, becoming more beige or pinkish at depth. The base of the deposit is weathered sandstone from the Mazeras Sandstone.
Typical Cross Section – Central Dune at Kwale
Mineral Resources & Ore Reserves Estimate
Location of Kwale Dunes
The Kwale Prospecting License comprises three mineralised zones, the Central, South and North Dunes, which occur as unconsolidated dunes. Only the Central and South Dunes currently form part of the Kwale Project.
The total Mineral Resources as at 30 June 2019 were estimated to be 285 million tonnes at an average HM grade of 6.0%. Within this, the Ore Reserve is estimated to be 62 million tonnes at an average HM grade of 2.3%. Mineral Resources and Ore Reserves are reported in compliance with the JORC Code (2012) standards and are summarised below.
The total Kwale Mineral Resources at 30 June 2019 are shown in the table.
|Deposit||Mineral Resource Category||Ore||In Situ HM||HM||Slime||Oversize||HM Assemblage|
The total Kwale Ore Reserves at 30 June 2019 are shown in the following table.
|Deposit||Ore Reserve Category||Ore||In Situ HM||HM||Slime||Oversize||HM Assemblage|
|Proved & Probable||-||-||-||-||-||-||-||-|
|Proved & Probable||62||2.3||3.8||27||3||57||13||6|
|Proved & Probable||62||2.3||3.8||27||3||57||13||6|
Read the full 2019 Mineral Resources and Ore Reserves statement.
Mining & Mineral Processing
The Kwale Project comprises the following major operational and ancillary components:
- Hydraulic mining unit (“HMU”)
- Wet concentrator plant (“WCP”)
- Slimes and tailings disposal
- Mineral separation plant (“MSP”)
- Product storage and shipping
- Power supply via a 14km 132 kV transmission line and substation
- Process water supply from a water storage dam on the Mukurumudzi River and additional groundwater sources
Utilising 3 HMUs, mined ore is fed by slurry pipeline to the WCP where the barren slimes and sand are removed to produce a heavy mineral concentrate (“HMC”). The HMC is delivered to the MSP for separation into three final products – ilmenite, rutile and zircon. The products are road hauled to the dedicated Likoni port facility where ilmenite and some rutile are stored for bulk loading into vessels. Zircon and the balance of the rutile are containerised and exported through the Port of Mombasa container terminal.
A simplified process flow diagram is presented below.
The Kwale Phase 2 (Stage 1) Project
The Kwale project was originally designed on the basis of treating the high grade Central Dune ore at a rate of 1,600 tonnes per hour.
To counter declining ore grades from mid-2018 and to fully exploit the MSP capacity, the project aimed to maximise HMC feed to the MSP by increasing mining rates in order to optimise production volumes for the remaining life of mine.
This was achieved by increasing mining and WCP capacities, along with upgrading water supply infrastructure to accommodate a mining rate of 2,400 tonnes per hour.
Successful commissioning of the uprated WCP was completed in April 2018 and dry dozer mining was simultaneously replaced by 3 HMUs, each with a capacity of 800 tonnes per hour.
The Kwale Phase 2 (Stage 2) Project
As the reserve in the Central Dune is depleted, the scope of Stage 2 involves the relocation of mining operations to the South Dune.
Engineering and design work commenced in mid-2018 and construction is scheduled for completion in June 2019. At a capital cost of US$12 million, it includes extension of 11kV power reticulation, installation of water and slurry booster pumps and pipelines and construction of a pipe bridge over the Mukurumudzi dam spillway.
The Kwale orebodies, comprising the Central and South Dunes, are eminently suited to hydraulic mining due to their high slimes content, which when mixed with water, creates a slurry that is capable of transporting sand and heavy mineral through trenches by gravity.
Water from the WCP is piped to each of three 800 tonnes per hour HMUs where its pressure is boosted and is then directed at the mining faces using monitor guns in order to excavate the ore and turn it into a slurry.
The slurry then gravitates through trenches to a pumping station from where it is transported to a centralised collection booster pump station and then to the WCP.
Compared to original system of dozer mining, hydraulic mining is a more cost effective approach for Kwale.
Wet Concentrator Plant
The WCP was initially designed for a maximum feed rate of 1,600 tonnes per hour and 140 tonnes per hour heavy mineral concentrate production. The Kwale Phase 2 upgrade increased WCP capacity to 2,400 tonnes per hour. The increased feed rate maximises HMC output and consequently ilmenite, rutile and zircon production as mining grades decline.
The slurried ore passes through a vibrating screen to reject +4mm trash materials with the undersize reporting to a large hopper. This slurry is then deslimed by pumping it through hydrocyclones to remove the barren fine clay or slimes present in the ore, typically accounting for 25-30% of total mass. The de-slimed sand is drawn from the surge bin and fed to a four stage wet gravity spiral circuit comprising banks of rougher, scavenger, cleaner and recleaner spirals to produce HMC and discard sand tails.
The primary cyclone overflow, containing the slimes fraction, reports to the thickeners. Flocculant is added to aid settlement of solids to generate a suitable slimes density in the thickener underflow for discharge to the TSF. Thickener overflow water is recovered and recycled back to process.
The sand tails were historically pumped to stackers to build the tailings storage facility (“TSF”) impoundment wall. This wall was competed in August 2018 and sand tails are now deposited in the mined out areas of the Central Dune as part of the mine rehabilitation programme.
Slimes Disposal and Impoundment
Removal of slimes from the sand before spiral plant treatment is essential, and effected by a hydrocyclone process. This demands a high volume of process water (about 50 gigalitres per year), much of which is recovered by recycling. The slime laden water is directed to two 38-metre diameter thickeners, dosed with a suitable flocculant and then separated into clear overflow water and thickened underflow slimes. The underflow has 30% to 36% solids content and is directed to the TSF for deposition, impoundment and solar drying.
Mineral Separation Plant
The MSP, located adjacent to the WCP, comprises the feed preparation circuit, the ilmenite separation circuit, the rutile dry circuit and wet and dry zircon circuits.
The plant operates at a maximum feed rate of 91 tonnes per hour of HMC, producing up to 455,000 tonnes ilmenite, 85,000 tonnes rutile and 32,000 tonnes zircon per annum. Changes in the ore mineral assemblage directly affect the ratio of these products recovered.
The HMC is upgraded using a combination of screening, electromagnetic, electrostatic and gravity separation techniques to generate marketable products of ilmenite, rutile and zircon. The ilmenite and rutile products are produced in bulk for sale to international markets, while zircon is typically bagged and containerised for export.
Rejected impurity streams are returned to the WCP for co-disposal with the sand and slimes tailings.
Likoni Marine Terminal
A dedicated bulk storage and shipping terminal has been established at Likoni, approximately 50km north of the mine site.
Ilmenite and rutile products are road hauled in bulk in conventional 30-tonne road trucks and discharged in the 80,000-tonne capacity storage shed at Likoni. A mobile ship loader utilising conventional conveyor technology loads at a rate of 800 tonnes per hour into bulk carrier vessels moored alongside the dedicated wharf. Zircon and some rutile are containerised on site and exported through the container terminal in the Port of Mombasa.
Base Titanium has constructed and commissioned an 8.5 million cubic metre water supply dam on the Mukurumudzi River to provide for the bulk of its process water requirements of about 29,000 cubic metres per day. The surface water supply is backed up by a bore field comprising 6 bore holes capable of supplying 9,500 cubic metres per day.
To provide for the bulk of its process water requirements of approximately 29,000 cubic metres per day, Base Titanium constructed and commissioned an 8.5 million cubic metre capacity water storage dam on the Mukurumudzi River. This supply is augmented with a bore field comprising 6 bore holes capable of supplying 9,500 cubic metres per day.
Grid power is supplied through a purpose built 14km 132kV power transmission line and main substation where it is transformed down to 11kV. Power required to run the operation is currently 15MW.
Access from the main A14 coastal highway to the mine site is by way of 8km sealed road built by Base Titanium.
To see how the project was built go to – Development History.