Summary

Deposit type

• Kimberlite

Summary:

Diavik mine is Diamondiferous kimberlite deposit.

The mineral resource and reserve for the Diavik Diamond Mine consists of four diamondbearing kimberlite pipes located under water in Lac de Gras. The pipes are relatively small, each having surface expressions less than 200 m in diameter, but they are high in grade. The kimberlite pipes that underpin the present mining plan are named A154S, A154N and A418. The fourth pipe, A21, is fully permitted for mining and in November 2014 received corporate approvals to commence the stages of construction toward its development as an addition to the mine plan.

Diamonds are generally included as xenocrysts in kimberlite magma as it is formed and ascends through the upper mantle and crust. As the earth’s surface is approached, the kimberlite magma, which is rich in volatiles such as CO2, erupts explosively to form the characteristic root-shaped pipe structure. Abundant kimberlite is erupted as pyroclastic ejecta and falls both within and adjacent to the pipe. The pipe is filled with a combination of pyroclastic kimberlite, hypabyssal kimberlite, and country rock that slumped back into the pipe. At Lac de Gras, the tops of the pipes were removed by continental glaciation. The kimberlites are softer than the surrounding rocks so that depressions were formed after the glaciers retreated and filled with water to become lakes. When the pipes occur under larger lakes, such as Lac de Gras, the pipes typically lie beneath small depressions on the lake bottom.

Mining Methods

• Blast Hole Stoping
• Sub-level Retreat

Summary:

Diavik is mining beneath its A21 open pit, which was closed in early 2023, as well as A154 diamond-bearing pipe, using blast-hole stoping and sub-level cave methods. The A418 underground kimberlite pipe was closed in the fourth quarter of 2022.

Diavik Diamond Mine has safely completed the development and construction of Phase 1 of the A21 underground mine, now moving the underground mine into commercial production. Building on the success of the first phase, Phase 2 of the A21 underground project was approved earlier this year with an additional investment of US$17 million. The project will enable Diavik to maximise the value from its known resources through to closure.

The Diavik Diamond Mine operates 24 hours per day, 365 days of the year. Crews at this remote site are resident on site while they work 12-hour shifts for 14 days, then rotate home for 14 days of rest. Four rotating crews cover 12-hour dayshifts, 12-hour nightshifts, on-site and off-site rotation.

Open pit
Mine design, planning and scheduling was based on 5 m intervals.

Benches in the two completed pits and pit A21 are 10m high. Catchment berms in the end walls were spaced every three benches, and the "triple benches" 30m walls were pre-cut (pre-split) in one 30m pass. The A154-A418 combined open pit was designed to supply 1.5 million tonnes per annum (Mt/y) of kimberlite and exceeded this soon after commissioning in 2003, peaking at 2.4 Mt/y during 2006–2008. The waste to ore ratio was relatively high, averaging 10 to 1 over the life of the pits. Total ore and waste production peaked at over 31 million tonnes per year and averaged 20–25 million tonnes per year for most of the time the two pits were shared.

Underground
Underground, blast-hole stopes are planned 25 m high and sub-level retreat stopes are also 25 m. Both mining methods take place simultaneously and multiple faces are in production from more than one level. Production ramp-up to the targeted steady-state output of 1.5–1.8 Mtpa ore took three years (2010–2012) as mine development in the granitic host rock pushed ahead to access additional ore faces. For 2013, Diavik’s first full year underground, the mine produced 1.9 Mt of ore and, with ore stockpiled from the open pit, processed 2.1 Mt. For 2014, 2.1 Mt of underground ore was mined and, with stockpiled ore, nearly 2.3 Mt was processed. Subsequent underground operating performance to the end of 2016 has been at similar levels.

For each of the pipes, pre-production stripping was carried out to remove lake-bottom sediments and glacial till (collectively referred to as overburden) that covered the bedrock and kimberlite pipe. Indistinguishable in the field and therefore mined as a single unit, the overburden was placed in a designated area so that it can be accessed and used in future for mine closure work.

Underground ore and waste is brought to surface at one of three portal entrances by underground haulage trucks and dumped on the ground in designated piles. The “portal muck” is then picked up by front-end loader and put onto surface haulage trucks (kept in service after the end of open pit mining) to be hauled either to the waste-rock dump (if waste rock) or to the ore processing plant.

Cemented rock-fill (“CRF”) is used as backfill underground. It is back-hauled into the mine (A154N only) from the nearby backfill plant by empty underground haulage trucks on their return trips.

Comminution

Crushers and Mills

Summary:

Crushing circuit consist of primary jaw crusher, secondary cone crusher and high pressure grinding rolls.

Processing

• Crush & Screen plant
• Dense media separation
• X-Ray sorting
• Grease belt/table recovery

Summary:

Diamond ore processing uses no chemicals to separate diamonds from kimberlite. The gravity-based methods used rely on the relatively heavier weight of diamonds to separate them.

Since 2015, two streams have been added to the coarse diamond fraction in recovery. In October 2014, a grease table was added to the -12 +6mm fraction that scavenged the rejects from the primary free-fall machines. In October 2016, an additional x-ray machine was installed that allowed the scavenging of the -30mm +6mm fractions (the entire range) of the primary freefall x-ray rejects.

In the recovery section of the plant, the diamonds are separated from the waste minerals using x-rays that trigger the unique characteristic of diamonds to glow. This triggers photo-electric sensors that direct strategically-placed air blasts to blow the diamonds into collection receptacles. Waste material is re-crushed if it is greater than a specific size otherwise the material is considered rejects and is stockpiled with a possibility to be reprocessed in future. The recovered stones then move through a series of sorters to the bottom of the processing plant where — under stringent security surveillance — an authorized employee measures and records the weight of the stones and also removes any non-diamonds.

Total recovery of all stones larger than the screen aperture has been the goal as small diamonds are economically viable for Diavik to recover. Grease tables have been incorporated into the recovery plant to support this. The screen size was 1 mm initially but has since been reduced to 0.85 mm. Nominal screen size is reported as 1 mm to provide a small allowance for wear.

The recovered diamonds are stored in a secured vault while waiting to be flown to Yellowknife for further cleaning and sorting. The diamonds are separated and packaged by size, weighed and stored in a special suitcase for shipping. The diamonds are flown discreetly but under security escort to the Diavik Diamond Mine’s product splitting facility (“PSF”) in Yellowknife where it is “split” by size and value into respective shares for the two Diavik Joint Venture entities. The PSF’s quality management system is ISO 9001 certified.

Water Supply

Summary:

The site is supplied with water from the Lac de Gras. The site has a type A water licence (W2015L2-0001) which allows for the withdrawal of up to 1.28 GL per year. The average long-term runoff for the associated catchment is estimated to be 197 GL per year.

Process water is recirculated and reused with minimal makeup water taken from Lac de Gras. Drinking water is drawn from Lac de Gras and chlorinated. A state-of-the-art sewage treatment plant for treating domestic sewage serves the entire site. All wastewater, mine water, seepages and surface run-off are impounded and treated before release back to Lac de Gras.

Mining is made possible by building water retention dikes and dewatering portions of the lake so that
mining can take place within the dewatered area.

All mine water — dike and pit wall seepage, inflows from the kimberlite and country rock mass, surface run-off, precipitation — is collected via ditches, sumps, pumps and pipelines for storage and treatment in the wastewater treatment plant.

Commodity Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Chief Operating Officer	Matt Breen		Mar 25, 2025
Infrastructure Superintendent	Caleb Larocque		Mar 25, 2025
Maintenance Superintendent	John Nauss		Mar 25, 2025
Sr. Production Manager	Kyle Buckoll		Mar 25, 2025
Surface Mining Superintendent	Joe Blandford		Mar 25, 2025