The bulk of mineralization currently defined on the Platosa project occurs as shallow to steeply dipping bodies of massive carbonate-replacement deposits (CRD). These bodies have been identified and categorized as discrete pods or mantos based on structural setting and concentration of sulphides. The main manto bodies currently defined at Platosa are listed below from west to east:
• Mantos 6A/6B
• Mantos 4A-C
• Manto 5
• Guadalupe
• Guadalupe South
• Pierna
• Rodilla
• Manto 623
• Manto 674
• NE-1
• NE-1 South.

The footprint of the Platosa manto system currently measures approximately 400 by 700 metres. Mantos at Platosa dip in accordance with the stratigraphy towards the east where a series of late extensional features down-drop the mineralization so that its depth ranges from 60 metres below surface on the west side of the mine to approximately 320 metres below surface at the NE-1 manto, on the east side of the mine.

The main lead-, zinc-, and silver-bearing minerals are:
• Galena (main lead-bearing mineral)
• Sphalerite (main zinc-bearing mineral)
• Acanthite and lesser proustite (main silver-bearing minerals). Acanthite is predominant;
proustite is visible where grades typically exceed the average grade of the mineralized body.

The most significant mantos at Platosa are the Rodilla, Pierna, Guadalupe South, Manto 674, and 623 mantos, which are currently mined; and the NE-1 and NE-1 south mantos, which are included in the mine plan and that are open for expansion. These mantos have been defined in drilling from surface with an average drill spacing of 15 to 20 metres. In 2016, Excellon commenced a program of infill and expansion drilling ahead of production. This drilling was conducted on 10-metre-spacing in production areas and has been successful in discovering and defining additional mineralization near existing mine infrastructure, most notably in the 623 and Guadalupe South areas.

Mineralization is also seen in the form of vein, breccia, and skarn systems.

The primary mining method has historically been a modified room and pillar, with the top of the manto being accessed first. For steeply dipping mantos, the area is benched down to a maximum height of 20 metres at which point a sill pillar is established. This process is repeated below the sill pillar until the bottom of the manto is reached. Historically, sill pillars were seldom necessary considering the flat- lying nature of the mantos, although these will become necessary where the mineralized body dips more steeply.

In 2018, Platosa transitioned the mining method to a cut and fill/drift and fill to increase the mining recovery. Engineering was completed for the construction of sill mattes composed of cemented rock fill (CRF) to eliminate the need for sill pillars in the future.

Primary stope accesses for cut-and-fill are driven into the deposit on a 15 percent decline. The bottom cut is mined, and the area is then backfilled with waste rock to facilitate extraction of the next cut. This sequence is repeated up to five times until the stope access reaches an incline of 15 percent. Access to the next cut is then provided by a 15 percent decline driven from a higher elevation. The mine plan anticipates that the cut and fill stopes will be backfilled with unconsolidated development waste, except for where a sill matte will be required when mining will occur directly below. Development waste from active headings as well as waste that has been stockpiled underground will be used to backfill the cut and fill stopes.

Historical pillars are being extracted, with previously mined areas supported with cable bolts. Each area is evaluated individually based on the rock quality and economic viability.

The completion of the dewatering project has allowed Platosa to increase mechanization. Jacklegs have been replaced with jumbos in certain production areas, improving safety and productivity. Platform bolting drills were purchased in 2018 to improve the safety and productivity of installing ground support compared to current methods using handheld drills.

Mineralized material is hauled to surface using one 20-tonne haul truck and three 16-tonne haul trucks. The mineralized material is placed at surface at either the low-grade or high-grade stockpile. A wheel loader transfers the material from the stockpiles into the crusher; the material is then crushed to less than 25 millimetres. The crusher is equipped with a stacker conveyor that permits loading of the crushed material directly into haul trucks or can divert it on the ground if a truck is not available. The crushed material is hauled in 40-tonne covered trucks to the mineral processing facility located at Miguel Auza, 220 kilometres away.

Crushed mineralized material from Platosa is shipped to the Miguel Auza processing facility, located 220 kilometres south of the mine. The Miguel Auza mineral processing facility operates two circuits: one for lead-silver and one for zinc-silver.

The Miguel Auza processing facility has been treating silver-, lead-, and zinc-rich CRD Platosa mineralization since 2009. The facility was initially designed and constructed to process material from the lower-grade Miguel Auza mine at a rate of 650 tonnes per day. Modifications were made in 2009 to ensure that the facility would be able to process the higher-grade feed; the flotation cells have been operating at 325 to 350 tonnes per day since that time. The unused cells are still on site and can be put back into production if required. The Miguel Auza processing facility currently produces two concentrates: a lead-silver and a zinc concentrate.

Crushing and Grinding
The Platosa 2,000 tonne-per-day primary jaw cr ........