There have been two ore-bearing structures mined at the Lucky Friday unit. The first, mined through 2001, was the Lucky Friday Vein, a fissure vein typical of many in the Coeur d’Alene Mining District. The ore body is located in the Revett Formation, which is known to provide excellent host rocks for a number of ore bodies in the Coeur d’Alene Mining District. The Lucky Friday Vein strikes northeasterly and dips steeply to the south with an average width of six to seven feet. Its principal ore minerals are galena and tetrahedrite with minor amounts of sphalerite and chalcopyrite. The ore occurs as a single continuous ore body in and along the Lucky Friday Vein. The major part of the ore body has extended from 1,200 feet to 6,020 feet below surface.

The second ore-bearing structure is known as the Lucky Friday Expansion Area, or Gold Hunter. It is located about 5000 feet northwest of the Lucky Friday workings and was discovered by Hecla in 1991. High grade silver mineralization occurs in steeply dipping veins hosted in a 200-foot thick siliceous lens within the Wallace Formation that transitions to the St. Regis Formation at about 5,900 feet below surface. We currently are mining at approximately 6,300 feet below surface. The veins are sub-parallel and strike west-northwest with a dip of 85 degrees to the south. The strike length of the mineralized package is approximately 2,150 feet. The 30 Vein, which contains higher silver grades, is the primary producer and represents approximately 57% of current proven and probable ore reserve tonnages, while the remaining 43% of reserves are contained in various intermediate veins having lower silver grades than 30 Vein. The width of 30 Vein ranges from approximately 0.5 feet to 15.4 feet, with an average width of approximately 7.4 feet.

Access to the mining horizons from the surface is by shaft access. Once underground, trackless drifts and ramps are utilized to reach the mining areas. An internal, hoisting shaft was completed in 2017 to extend access at depth in the Gold Hunter area. The principal mining methods in use at the Lucky Friday unit consist of underhand systems with integral paste fill and varying degrees of mechanization. The most prevalent system in use in 2020 was underhand cut and fill. This method utilizes rubber-tired equipment to access the veins through ramps developed outside of the ore body. Once a cut is taken along the strike of the vein, it is backfilled with cemented tailings and the next cut is accessed below from the ramp system. In 2020, we began testing a new underhand method that has the potential for increased mechanization. It is akin to longhole stoping but is conducted over shorter vertical intervals and without an undercut. Work has been underway since 2017 to develop a fully mechanized underhand method which would utilize a remote vein miner for mechanical excavation. Fabrication of the remote vein miner was completed in 2019. Testing and modification of the machine at the manufacturer's facilities proceeded in 2020 but has been delayed by COVID-19. Delivery to Lucky Friday is expected in 2021.

Crushing
Run of Mine ore discharges into one of two coarse ore bins with capacities of 400 and 800 tons. The ore discharges from the bottom of the bins metered by pan feeders and a belt scale is used to control feed rate to the crushing circuit. Coarse ore is crushed in a three stage crushing plant consisting of a primary jaw crusher, a standard secondary crusher, and short head tertiary cone with a triple deck screen to close the crushing circuit. Crushing circuit operating time averages about 50 percent with an average throughput rate of 80 to 85 tons per operating hour.

The primary crusher, a 20 X 36 inch jaw crusher, reduces run of mine ore from minus 12 inch to minus 3 inch. Primary crushed ore is delivered to a triple deck vibrating screen for sizing. Coarse material is conveyed to the secondary crusher and is reduced to one inch minus in a 3 foot standard cone crusher. A magnet removes metal from the secondary feed to prevent it from damaging the crusher. The oversized material from both the middle and bottom deck of the triple deck screen is conveyed to a 3 foot short head crusher. A second magnet prevents metal from entering the short head crusher. Both the standard and short head crusher discharge returns to the triple deck screen to be reclassified. All material leaving the crusher circuit reports to a 400 ton fine ore bin with 100% passing the 3/8 inch screen. Dust from the crushing area is controlled by a bag house.

Grinding
Material from the fine ore bin is discharged by two hydraulic feeders. A feed sample is collected from a transfer point of two belts by a primary automatic cutter and then through a secondary cutter for a 12 hour shift composite sample. The fine ore then passes over a belt scale for determining feed rate to the ball mill. Fine ore, reagents, cyclone underflow, and water feed the ball mill. Overall mill operating time averages 92 percent and from 2007 to 2013 and the average annual mill feed rate ranged from 40.0 to 43.6 dry short tons per hour.

The ore is ground in one 9.5 x 12-foot ball mill driven by a 600 hp motor. Ball mill discharge combines with water, collector, and frother and then is pumped to a SK-240 Pb flash flotation unit cell. Flotation reagents are added to the flash cell tailing and the pulp is pumped to a cyclone cluster for classification. Cyclone overflow is screened to remove trash and then pumped to the Pb rougher circuit. Cyclone underflow returns to the ball mill. The cyclone overflow is typically forty percent solids with a particle size of 80 percent passing 150 microns.

The flash flotation cell is used to recover coarse fractions of Pb and Ag from the mill circulating load to minimize over grinding of the dense materials. The flash cell has proven to be capable of producing a final concentrate grade product, assaying roughly 63% Pb and 100+ oz/ton Ag. Typically around 50% of the Pb and Ag values are recovered to final concentrate through this route. Another benefit of the flash flotation unit cell is freeing up flotation capacity in the Pb circuit. When high grade ore is processed through the mill, this increased capacity is realized fully.

Ore at the Lucky Friday unit is processed using a conventional lead/zinc flotation flowsheet. Run of mine ore is crushed in a conventional three stage crushing plant consisting of a primary jaw crusher, followed by secondary and tertiary cone crushing circuits. Crushed ore is ground in a ball mill, and the ground slurry reports to the lead flotation circuit. The lead circuit tailings report to the zinc flotation circuit. Lead and zinc concentrates are thickened and filtered, and concentrate products are shipped to smelters for final processing. The original flotation mill was constructed in 1960 and had a capacity of 750 tons per day. Various modifications and upgrades have been made since that time, and the plant capacity currently is estimated at 1,000 tons per day. Total mill recovery was approximately 96% for silver, 95% for lead and 91% for zinc during 2020. All lead and zinc concentrate sales during 2020 were shipped to Teck Resources Limited's smelter in Trail, British Columbia, Canada.

Flotation
The Pb rougher flotation consists of one bank of five WEMCO 66D conventional flotation cells. Concentrate from the roughers, containing about 38% Pb, reports to the first cleaner column cell while the tailings gravity flow into a bank of four Denver DR-24 conventional flotation cells for Pb scavenging. Reagents for collecting, frothing, and conditioning are added to the slurry as needed. Pb scavenger concentrate is pumped back to the roughers and the Pb scavenger tailing are fed to the Zn flotation circuit.

Slurry reporting to the Pb first cleaner is upgraded from roughly 38% Pb to around 50% Pb and the first cleaner concentrate is pumped to the second cleaner column. Tails from the first and second column are combined and pumped to a set of four Denver 21 conventional flotation cells for cleaner scavenger duty. Cleaner scavenger concentrate is pumped to the third cleaner column while the tails are pumped to the Pb rougher feed. Concentrate from the third column normally returns to the first column for upgrade and the tails are pumped to the Pb rougher feed. Final Pb concentrate from the second cleaner column and the flash cell concentrate average 63% Pb and 100 oz Ag per ton. Before reporting to the thickener, the Pb concentrate passes through a primary and secondary sampler.

Pb circuit tailings are mixed with reagents to activate the Zn in the two conditioning stages and flow by gravity to the Zn rougher flotation circuit. Flow rate through the two conditioner tanks is designed such that adequate retention time in each tank is maintained for the reagents to fully condition the slurry for Zn flotation. The second conditioning tank overflows into the Zn flash flotation cell. The concentrate from the flash flotation cell is pumped directly to the first column essentially making it the first rougher in the Zn circuit.

The tailing from the Zn flash flotation cell is pumped to the feed end of the Zn rougher flotation bank where the Zn circuit mirrors the Pb circuit except the third cleaner column cell concentrate reports to the final concentrate thickener. Both Pb and Zn circuits utilize the same size rougher, scavenger, and cleaner scavenger cells. Tailings from the Zn circuit, barren of most valuable metals, are pumped to the final tailings system.

Concentrate Dewatering
After Pb and Zn concentrates have passed through their respective samplers they enter the center well of the final concentrate thickeners. The Pb and Zn concentrate handling systems are mirrored like the flotation circuits. Both thickeners are twelve foot diameter high-rate solid-liquid separators producing a bed of solids in the cone of the thickener. Concentrate thickener underflow at about 60% solids is pumped to the concentrate filters. Overflow water from the thickener reenters the flotation circuit as spray water in the froth launders. Separate Pb and Zn spray water systems are installed.

The paste discharging from the thickener is pumped by air powered diaphragm pumps to vacuum drum filter for each product. Pb concentrate is filtered by a drum filter equipped with a vacuum pump for dewatering to less that 8% moisture. Zn concentrate is dewatered to around 6% moisture using the same method as the Pb concentrate filter. The dry filter cake concentrate falls off of the filter drum into a bunker directly below it. Pb/Ag concentrate and Zn concentrate are shipped in highway trucks to a smelter daily for further processing and refining.