Big River Gold : Mica Testwork Progress Report

ASX RELEASE

22 September 2020

MICA TESTWORK PROGRESS REPORT

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• Testwork continued successfully with Nagrom in Perth to develop potentially commercial mica concentrates for sale as a by-product for the Borborema Gold Project.
• Work is ongoing but work to date:
• • Have produced concentrates suitable for commercial application in the plastics filler industry;
  • Show that simplifying the process by removing the de-sliming stage has resulted in a 25% increase in the mass yield for the concentrates.
  • Have produced high quality concentrates with a lesser number of magnetic separation stages, potentially reducing capital and operating costs.
• Covid 19 restrictions have delayed the completion of testwork for plasticity and other physical parameters. Upon receipt of those results the Company will be able to provide

concentrate details to potential offtake counterparties.

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Big River Gold Ltd (ASX:BRV) (the Company or Big River) wishes to advise that a significant stage of the analysis being undertaken to assess the commercial viability of mica production at the Company's 100% owned Borborema Gold project, has been completed by Nagrom in Perth, WA with positive results.

The program currently being undertaken by Nagrom follows on from the testwork completed successfully by Dorfner Analysenzentrum und Anlagenplanung Gmbh (ANZAPLAN in Germany (refer ASX announcement of 18 February, 2020). The aim of Nagrom's work is to produce a commercially viable bulk concentrate in the first instance of which details of the chemical and physical properties can be made available to potential distributers or other offtake counterparties.

Potential scale of mica by-product production

The Borborema ore body contains very significant quantities of auriferous mica that will be processed through its planned 2Mtpa CIP process plant1. Initial work showed that after processing through the milling, cyanide leach and elution circuits, a substantial amount of mica could be readily separated by magnetic separation. This product retained attractive commercial chemical and physical properties including flake size and importantly, being free of deleterious crystalline silica (quartz). Refer to the attached data sheet in Appendix 1 for more details.

Magnetic separation represents a technically simple, low cost and chemical free process that could be readily included or retro-fitted to the currently designed gold plant to process the dry tails.

Appendices 1 and 2 (attached) provide details of the sample selection, their locations and the subsequent preparation and metallurgical testwork.

1 ASX Announcement 9 July 2020. DFS Review significantly upgrades Borborema project.

Potential applications for this type of product are in the large volume plastic filler market, (in particular dark coloured polymers). Other uses could be for coatings and in the paint market where it would serve as a key additive with anti-corrosive properties. The 2018 pricing for a wet ground fine mica concentrate of this type from the USA was US$300 - US$500/tonne2.

Figure 1. Picture showing the gold plant leach residue (left), non magnetic reject (centre) and mica rich magnetic concentrate (right)

Figure 2. Magnetic mica under optical microscope - size on lower right

Progress to date

All of the work in Nagroms scope was completed in August. Additional testwork investigating the physical and plasticity characteristics is being completed by Microanalysis Ltd in Perth after some delays in receiving the samples due to Covid19 restrictions. A Technical data Sheet (TDS) will be made available for the market at that time.

The samples assessed by Nagrom are the same metallurgical composites that were used for the Definitive Feasibility Study (DFS) and the ANZAPLAN work. Details of the composites including source, locations and chemical analyses are provided in Appendix 1.

Below is a progress report on the results achieved by Nagrom which were very encouraging.

1. Removal of the desliming stage increases product mass yield by 25%

• The only additional sample preparation undertaken by Nagrom resulted in a comparison of the benefits of removing the slimes, or ultra fine particles, from the composite to produce the concentrate (as was done by ANZAPLAN). Nagrom repeated the testwork to investigate whether or not to incorporate a desliming stage before magnetic separation with results summarised in Table 1.

2 Statistica Industrial Minerals Market Information: https://www.statista.com/

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Table 1. Production of concentrate with and without desliming stage.

Master Composite with Desliming

Product	Yield	Fe2O3		K2O		A12O3		SiO2
	(%)	(%)		Dist	(%)		Dist.	(%)	Dist	(%)		Dist
Final Con.	13.5	21.2		40.6	7.0		29.9	18.2	17.3	37.0		7.7
Master Composite without Desliming
Final Con.	16.8	20.6		47.2	6.8		36.0	18.8	21.0	38.0		10.0

• A final grade mica concentrate was achieved that is equivalent or slightly better than that produced by ANZAPLAN and by removing the desliming stage provides a 25% increase in mass yield to 16.8%.

2. Processing path simplified with fewer magnetic separation stages.

• Nagrom commenced testwork using the same process stages and initial flowsheet as was used by ANZAPLAN but found that final product grade could be achieved after 3 stages cleaning with magnetic separators compared with 6 which were used by ANZAPLAN
• The Nagrom magnetic separation circuit is much less complex and the reduction in the number of stages will result in operational efficiencies.
• Table 2 summarises the results of cleaning the cyclone underflow composites so that the amount of potassium (as K2O) that reports to the non-magnetic fraction is minimised. Potassium is the key indicator for phlogopite which is the desired mica mineral in the magnetic fraction that will be produced for possible sale. The results show that the composites for Cleaner 4 and 5 non-magnetic and Cleaner 5 magnetic fractions have similar concentrations. This demonstrates that further improvement in mica recovery to the potentially saleable concentrate did not occur after the third magnetic separation stage as a result of Nagrom using magnetic separation equipment that is better able to process very fine particles.

Table 2. Cleaning of cyclone underflow composites (Non mag fraction)

	Non-magnetic fraction	Mass (kg)	Fe2O3 (%)	K2O (%)	Al2O3 (%)	SiO2 (%)*
	Original sep fraction	6.588	2.094	1.333	12.424	76.452
	After Cleaner 1	1.014	7.988	4.122	17.564	58.050
	After Cleaner 2	0.491	12.269	5.908	20.101	47.739
	After Cleaner 3	0.456	15.650	6.802	20.540	41.511
	After Cleaner 4	0.298	17.120	6.888	20.283	39.899
	After Cleaner 5	0.265	17.913	7.089	20.143	39.212
	Cleaner 5 mag fraction	1.302	21.402	7.043	19.057	36.169
	*Non crystalline silica

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3. Concentrate can be produced using conventional fine grind.

• Nagrom have demonstrated that the use of conventional fine grinding equipment is able to produce a product that has a similar article size to that sold into the plastic and polymer markets (refer Table 2).
• the anticipated production of a commercially attractive mica concentrate at Borborema is expected to employ conventional and relatively simple technology. This will primarily incorporate magnetic separation which will be chemical free and require only power consumption at an estimated site cost of $0.08/kWhr3.

Investors should note that at this stage the commercial acceptance and establishment of sales contracts for this concentrate product has yet to be determined and is will be the subject of ongoing market investigation.

Commercialisation and market for mica.

Further testwork is being planned to investigate:

1. technical acceptance in the above markets in line with the testwork results. TDS's will be produced and provided to 10-20 potential customers for commercial assessment;
2. Feedback from potential customers as to what changes to the product specifications might be required to meet alternative applications end uses, and
3. the separation of coarse flaked phlogopite (high magnesium biotite) from the bulk concentrate for use in the specialist electronics and automotive industries. The presence of coarse flake phlogopite has been noted and separation of even small quantities of this material will be significant due to its very high value.

The mica market is specialised and relatively small requiring careful management to establish offtake without disrupting the market. However, Borborema does offer the market good quality product derived from ethical mining practices not always present in this sector4. In conjunction with supplying samples to prospective customers, Big River will carry out a market study aimed at identifying markets for the product within Brazil and internationally.

Table 3. Uses, scale and potential significance of mica products

	Product (Various			Global Market			Indicative
			Annual			price range.			Uses
	classes)
			Capacity			US$/tonne1
	Coarse		300 - 500,000		US$200 -		Electronics, high-end cosmetics, metallic (auto) paints, rubber &
	phlogopite-rich		tonnes		US$1000		plastic compounds, brake linings
	Bulk mica		~3 million		US$300-		Excellent electrical and electronic performance, fillers and
	(muscovite-		tonnes		US$500		extenders in a variety of rubber compounds and adhesives,
	biotite)								insulation, automotive plastic compounds, paints, lubricants,
										electrical capacitors, gypsum wallboard, oil drilling muds, some
										soaps and cosmetics, insulation, glitter, faux jewellery etc

1. Definitive Feasibility Study, December 2019 (ASX Announcements and 23 December 2019 and 8 July 2020)
2. Global Mica Mining, and the impact on childrens rights. Terre des Hommes, SOMO. March 2018

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