Operational Update - Mokopane Tin Project

RNS Number : 6206B

Bushveld Minerals Limited

20 June 2016

 

20 June 2016

Bushveld Minerals Ltd

("Bushveld" or the "Company")

Operational Update -  Mokopane Tin Project

Bushveld Minerals Limited (AIM: BMN), a diversified mineral development company with a portfolio of vanadium, titanium, iron ore, tin and coal assets in Africa, is pleased to present results from pilot-scale metallurgical test work and plant design at its Groenfontein Tin Deposit ("Groenfontein Deposit" or the "Deposit") in Limpopo Province, South Africa. 

Highlights

The Groenfontein Deposit test work was intended to assess tin recovery on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flow-sheet design parameters. The test work has delivered the following positive results:

·      Expected recovery using gravity concentration of over 70%, for grind sizes of -1 mm;

·      Achieved commercial concentrate grade of 74.59% SnO₂ (cassiterite - equivalent to 58.75% Sn);

·      Plant design and flowsheet underway; 

·      Final costing underway to determine capital and operating expenditure requirements for mining and processing plant establishment, together with ancillary infrastructure; and

·      Results to be incorporated into an updated business model focusing on the smaller-scale, near surface high-grade tin targets near-term production.

Bushveld released a scoping study on the Groenfontein and Zaaiplaats deposits in September 2014, which envisaged a mining rate of 691,000 tons per annum at a head grade of 0.12-0.23% SnO₂ to produce 610-1130 tons of refined tin metal per annum post smelting.

Pursuant to the 2014 Scoping Study, the Company decided to revise the development plan for the project to focus on mining the higher-grade zone of the Groenfontein and Zaaiplaats Deposits and processing it using a relatively simple gravity separation flowsheet to produce a saleable concentrate product. The scope revision was driven by the Company's interest in executing a low capex near term production operation. The aim is to take advantage of a relatively buoyant tin market and establish Greenhills as a stand-alone tin asset.

In order to assess tin recovery parameters on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flowsheet design parameters, a large (500 kg) sample of surface ore from historical workings at the Groenfontein Deposit was submitted for additional metallurgical test work at Peacocke & Simpson, minerals processing experts specialising in gravity recovery.

The results show that at a top size of 1 mm, >70% Sn recoveries are achieved for enhanced gravity concentration, less than 15% Sn is lost to tailings during spiralling, and shaking tables achieve at least 85% recovery, giving over 50% cumulative recoveries and a final concentrate grade of 74.59% SnO₂ (58.75% Sn).

Consequently, a flowsheet has been developed for gravity separation, with crushing and screening and rod-milling to -1 mm. Material is concentrated via spirals and shaking tables to maximise recovery and SnO₂ concentrate grade. The plant design envisages a 164,160 tpa operation producing up to 510 tpa SnO₂.

The next step is to complete flowsheet design and mine-planning studies to determine mine capex and opex parameters, which will be incorporated in a revised financial model.  

Fortune Mojapelo, CEO of Bushveld Minerals, said: "The encouraging metallurgical results achieved support our view that high-grade cassiterite concentrates can be produced from the Groenfontein Deposit with relatively good recoveries. With recently updated plant capex and opex estimates at hand, we look forward to finalising infrastructure and mine cost estimates while continuing to focus attention on accelerating smaller-scale mine development and commissioning. The tin market has been particularly positive in a generally negative commodity environment with the tin price up 18% since the start of the year on supply constraints."

Enquiries: [e-mail]

Bushveld Minerals Fortune Mojapelo	[phone]
Strand Hanson Andrew Emmott	[phone]
Mirabaud Securities Rory Scott	[phone]
Beaufort Securities Limited Jon Belliss	[phone]
Tavistock Jos Simson/ Nuala Gallagher	[phone]
Lifa Communications Gabrielle von Ille	[phone]

- ENDS -

Notes to editors

Bushveld Minerals Limited is a diversified mineral development company with a portfolio of vanadium, iron ore, tin and coal assets in Southern Africa and Madagascar.

The Group owns the Bushveld Vanadium Project, Mokopane Vanadium Project, Bushveld Iron Ore Project and Mokopane Tin Project, located on the northern limb of the Bushveld Complex, South Africa. Bushveld also owns the Imaloto coal project in Madagascar, acquired in September, 2015, through its takeover of Lemur Resources.

Bushveld was admitted to the AIM of the London Stock Exchange in March 2012.

BULK SAMPLE PILOT TESTWORK

As a follow-up to metallurgical testwork reported in the Groenfontein Deposit Scoping Study, a large (500 kg) ore sample from the Groenfontein Deposit was submitted for additional metallurgical testwork at Peacocke & Simpson, minerals processing experts specialising in gravity recovery. This testwork informed final flowsheet parameters and plant design at Appropriate Processing Technologies (APT), who would be fabricating the plant.

Testwork was designed to emulate a multi-stage gravity processing plant, and included enhanced gravity pre-concentration (Stage 1), spiralling (Stage 2) and cleaning of recovered cassiterite into high-grade concentrates via shaking tables (Stage 3). At each stage, concentrates, middlings and tailings were assayed in order to understand mass-pulls and to fine-tune plant design.

The results show that at a top size (p80) of -1 mm, >70% Sn recoveries are achieved for enhanced gravity concentration, >85 % Sn reports to middlings and concentrate during spiralling, and shaking tables achieve at least 85% recovery, giving >50% cumulative recoveries and a final concentrate grade of 74.59% SnO2 (58.75% Sn).

Details of the various stages of pilot plant testwork are described below.

A - Enhanced Gravity Concentration

The bulk ore sample was crushed and screened on a 1 mm test sieve, and the crushed product was pulped with water and treated using a Knelson CVD6 concentrator. 4 stages of concentration were carried out, with tailings from earlier stages being run through the concentrator in later stages

The results of the enhanced gravity concentration are as follows:

Table 1: Knelson CVD concentration

Stage	Conc. Mass (kg)	Conc. Mass (%)	Cumulative Conc. Mass (%)	Sn Grade (%)	Cumulative Sn Grade (%)	Sn Recovery (%)	Cumulative Sn Recovery (%)
CVD 1	65.01	13.0	13.0	3.37	3.37	71.2	71.2
CVD 2	61.5	12.3	25.3	0.41	1.93	8.2	79.4
CVD 3	62.4	12.5	37.8	0.30	1.39	6.1	85.5
CVD 4	67.00	13.4	51.2	0.20	1.08	4.3	89.8
CVD Tailings	244.09	48.8	100.0	0.13	0.62	10.2	100.0
Head Grade	500.0	100.0		0.62		100.0

Note that Stage 1 achieves a 71.2% recovery and a grade of 3.37% Sn at a 13.0% mass yield, and whilst recovery increases to 89.8% after 4 stages, the cumulative recovered grade drops to 1.08% and cumulative mass yield increases to 51.2%. This suggests that a significant amount of the cassiterite is well-liberated at -1 mm, and progressively lower recovered Sn grades in stages 1-4 indicates recovery of impure (i.e. partially liberated) cassiterite. This corroborates previous metallurgical testwork at SGS (Announced December 2012) suggesting good liberation of cassiterite at >212 microns.

B - Spiralling

Following recovery of concentrates produced via enhanced gravity separation, these concentrates were subjected to further upgrading via spiralling. Each CVD concentrate was processed separately on spirals to produce three streams - concentrate, middlings and tailings. Results are summarised in Table 2.

Table 2: Spiralling results

Conc.	Tailings Mass (kg)	Tailings Sn Grade (%)	Sn Fraction in Tailings	Middlings Mass (kg)	Middlings Sn Grade (%)	Sn Fraction in Middlings	Conc Mass (kg)	Conc Sn Grade (%)	Sn Fraction in Conc
CVD 1	46.298	0.66	13.9	13.635	8.89	55.3	5.077	13.3	30.8
CVD 2	51.961	0.24	49.7	7.935	0.56	17.6	1.604	5.16	32.7
CVD 3	55.345	0.23	67.8	4.478	0.22	5.2	2.577	1.98	27.1
CVD 4	60.538	0.15	69.3	4.570	0.21	7.1	1.892	2.71	23.5

These results show that the first enhanced gravity concentrate (CVD1) gives the lowest loss of Sn to the tailings, and the highest fraction of tin in the concentrate and middlings. With subsequent CVD concentrates, tin recovery to middlings and concentrate get significantly lower, and only 30.7% of tin is recovered by spiralling the CVD 4 concentrate. This confirms the earlier inference that the majority of well-liberated cassiterite is recovered during the initial enhanced gravity stage, and that later stages recover partially liberated cassiterite.

C - Tabling

In a typical gravity-based ore mineral beneficiation plant, shaking tables are used as a final stage in order to produce a clean (pure) concentrate.  During stage 3, concentrates from stage 2 were upgraded on a shaking table in order to produce final concentrates.  These results are summarised in Table 3.

Table 3: Shaking table results

Conc.	Tailings Mass (kg)	Tailings Sn Grade (%)	Sn Fraction in Tailings	Middlings Mass (kg)	Middlings Sn Grade (%)	Sn Fraction in Middlings	Conc Mass (kg)	Conc Sn Grade (%)	Sn Fraction in Conc
CVD + Spiral 1	3.844	0.36	1.95	0.46	18.38	12.66	0.773	74.59	85.39
CVD + Spiral 2	1.156	0.23	3.36	0.25	5.19	15.60	0.198	33.88	81.04
CVD + Spiral 3	2.235	0.23	9.96	0.196	8.78	33.57	0.146	19.72	56.47
CVD + Spiral 4	1.524	0.18	8.51	0.286	3.36	30.64	0.082	23.19	60.85

The concentrate mass, tin fraction and grade is highest for the 1^st round CVD + Spiral tabled concentrate, and decreases in subsequent stages, reflecting the fact that 1^st stage concentrates have more well-liberated cassiterite particles than latter stages. This is also reflected by the increase in the Sn fraction lost to the tailings in later stages.

Implications for Flow Sheet Configuration and Plant Design

The aim of the testwork was to finalise the configuration of a flow sheet to maximise the recovery. Owing to the excellent recovery (>70%) of cassiterite with a 1^st pass on the CVD, it is unlikely that further passes will be required - however, for small plant sizes (<30tph), the CVD would likely be replaced with a rougher spiral. It is expected that overall Sn recoveries through the plant will be in excess of 70%.

 

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