Overview

Deposit type

• Epithermal
• Volcanic hosted
• Vein / narrow vein

Summary:

Based upon the styles of alteration, the nature of the veins, the alteration and vein mineralogy, and the geologic setting, the gold and silver mineralization at the DeLamar project is best interpreted in the context of the volcanic-hosted, low-sulfidation type of epithermal model. This model has its origins in the De Lamar - Silver City district, where it was first developed by Lindgren (1900) based on his first-hand studies of the veins and altered wallrocks in the De Lamar and Florida Mountain mines. Various vein textures, mineralization, and alteration features, and the low contents of base metals in the district are typical of what are now known as low-sulfidation epithermal deposits world-wide.

The DeLamar project is situated in the Owyhee Mountains near the east margin of the mid-Miocene Columbia River – Steens flood-basalt province and the west margin of the Snake River Plain. The Owyhee Mountains comprise a major mid-Miocene eruptive center, generally composed of mid-Miocene basalt flows intruded and overlain by mid-Miocene rhyolite dikes, domes, flows and tuffs, developed on an eroded surface of Late Cretaceous granitic rocks.

The DeLamar mine area and mineralized zones are situated within an arcuate, nearly circular array of overlapping porphyritic and flow-banded rhyolite flows and domes that overlie cogenetic, precursor pyroclastic deposits erupted as local tuff rings. Integra interprets the porphyritic and banded rhyolite flows and latites as composite flow domes and dikes emplaced along regional-scale northwest-trending structures. At Florida Mountain, flow-banded rhyolite flows and domes cut through and overlie a tuff breccia unit that overlies basaltic lava flows and Late Cretaceous granitic rocks.

Gold-silver mineralization occurred as two distinct but related types: (i) relatively continuous, quartzfilled fissure veins that were the focus of late 19th and early 20th century underground mining, hosted mainly in the basalt and granodiorite and to a lesser degree in the overlying felsic volcanic units; and (ii) broader, bulk-mineable zones of closely-spaced quartz veinlets and quartz- cemented hydrothermal breccia veins that are individually continuous for only a few meters/feet laterally and vertically, and of mainly less than 1.3 centimeters (0.5 inches) in width – predominantly hosted in the rhyolites and latites peripheral to and above the quartz-filled fissures. This second style of mineralization was mined in the open pits of the late 20th century DeLamar and Florida Mountain operations, hosted primarily by the felsic volcanic units.

The fissure veins mainly strike north to northwest and are filled with quartz accompanied by variable amounts of adularia, sericite or clay, ± minor calcite. Vein widths vary from a few centimeters to several meters, but the veins persist laterally and vertically for as much as several hundreds of meters. Principal silver and gold minerals are naumannite, aguilarite, argentite, ruby silver, native gold and electrum, native silver, cerargyrite, and acanthite. Variable amounts of pyrite and marcasite with very minor chalcopyrite, sphalerite, and galena occur in some veins. Gold- and silver-bearing minerals are generally very fine grained.

The gold and silver mineralization at the DeLamar project is best interpreted in the context of the volcanichosted, low-sulfidation type of epithermal model. Various vein textures, mineralization, alteration features, and the low contents of base metals in the district are typical of shallow low-sulfidation epithermal deposits worldwide.

Mining Methods

• Truck & Shovel / Loader

Summary:

Mining will utilize 23-cubic meter (30-cubic yard) hydraulic shovels along with 13-cubic meter (16.7-cubic yard) loaders to load 136-tonne capacity haul trucks. The haul trucks will haul waste and ore out of the pit and to dumping locations. Due to the length of ore hauls, the ore will be stockpiled near the pits followed by loading into a Railveyor system which will convey the ore into a crusher. The Railveyor system will be supplemented with haul trucks on an as needed basis.

Waste material will be stored in waste-rock storage facilities (“WRSFs”) located near each of the Florida Mountain and DeLamar deposits, as well as backfilled into pits where available. The exception is the Milestone pit, from which waste material will be fully utilized for construction material for the tailing storage facility (“TSF”).

The production schedule considers the processing of Florida Mountain oxide and mixed material by crushing and heap leaching. Florida Mountain non-oxide material would be processed using flotation followed by cyanide leaching of the flotation concentrate. Processing of the DeLamar material will require crushing and agglomeration prior to heap leaching and non-oxide material will be processed through the mill.

Monthly periods were used to create the production schedule with pre-stripping starting in Florida Mountain at month -5. The start of leach processing is scheduled in month 1, though a total of 610,000 tonnes of leach material is to be mined during preproduction. It is assumed that this material will be crushed and used as over liner on top of the leach pad liner. The nominal rate for leach processing will be 35,000 tonnes per day or 12,600,000 tonnes per year. Note that during the first year, a total of 10,287,000 tonnes will be processed along with the material laid onto the pad during preproduction. This represents a ramp up to full processing.

Leaching starts with Florida Mountain material in month 1 and DeLamar leach material is processed starting in year 2. Prior to that, the agglomeration circuit will be installed. The DeLamar leach material will be processed up to the same rate as the Florida Mountain material.

Florida Mountain and DeLamar non-oxide material will be stockpiled until the flotation mill is constructed. The start of the 6,000 tonne per day mill will be in year 3 with 1,982,000 tonnes processed in that year, increasing to 2,160,000 tonnes per year after that until the non-oxide material is exhausted.

The total mining rate would ramp up from an initial 2,000 tonnes per day to about 60,000 tonnes per day over a period of six months. A maximum of 138,000 tonnes per day is used in later years when the stripping requirement becomes more significant in Florida Mountain phase 3.

The mine is anticipated to operate 24 hours per day, utilizing four crews of workers each working four days on and four days off. It is anticipated that these crews would rotate between day shift and night shift. The daily shift schedule would be 12 hours per day reduced to account for standby time including startup/shutdown, lunch, breaks, and operational delays totaling 3.0 hours per day. This allows for 21 work hours in each day or 87.5% schedule efficiency.

Pioneer drills would be smaller air-track drills with contained cabs and the production drills are anticipated to be 45,000lb-pulldown, track-mounted, rotary blast-hole drills. An 83% efficiency factor was used for pioneer drilling and 85% efficiency was used for production and controlled blast-hole drilling. Penetration rates of 26.3, 27.5, 30.3 meters per hour (86.3, 90.2, 99.4 feet per hour) were used along with 2.8, 2.8, and 3.0 minutes per hole of non-drilling times for production, trim-rows, and pioneer drilling, respectively.

Based on the parameters used, one pioneer drill and five production drills are estimated to be needed. It is assumed that these drills will last through the life of mine (“LOM”) with an availability of 85% for the life of the drill.

Loading equipment is anticipated to include one large 13-cubic meter (17 cubic yard) loader and two 23-cubic meter (30 cubic yard) hydraulic shovels. The loader theoretical productivity was estimated to be 2,345 tonnes per hour, or 1,950 tonnes per hour at an operating efficiency of 83%. The loader is primarily used for back-up mining production and re-handle of material from stockpiles. The assumed availability starts at 90% and is reduced 1% per year until it reaches 85%, and then is held constant through the life of the loading units. No replacement loaders were assumed. The overall use of available hours is 33%.

Two hydraulic shovels are used as the primary loading tool. The initial shovel starts operating in month -6 and the second shovel starts working in month 1. The theoretical productivity was estimated to be 3,326 tonnes per hour, or 2,760 tonnes per hour after applying 83% efficiency. As with the loader, the assumed availability starts at 90% and declines at 1% per year to a low of 85%, and then remains the same through the LOM. The overall use of operating hours is 80%.

Haul trucks are assumed to be 136-tonne capacity rigid frame trucks. Haulage hours were developed using MineSched software (Version 2021). MineSched uses 3-dimensional centerlines drawn for bench, in-pit, and ex-pit travel. The performance and retard curve data are input into the software, and MineSched uses that along with the truck capacity and load, dump, and spot times to determine the time required to haul material to its destination. The hours developed from MineSched are considered productive hours, and these are adjusted in the mining cost spreadsheets to include an 83% efficiency.

The loading time provided in the software is based on the hydraulic shovel and are included in the productive hour calculation. This is adjusted in spreadsheets to reflect the use of loaders; thus the load time is dependent on whether the truck was loaded by a loader or shovel. The loader time used was 3.73 minutes and the shovel time used was 2.70 minutes. Spot time at the loader or shovel was 0.50 minutes and the spot and dump time was a combined 1.20 minutes. A capacity of 131 tonnes per load was used as dry tonnage to reflect the dry densities in the resource block model. The number of trucks was calculated to increase over time due to farther haulage with some pit phases. A total of 16 haul trucks are purchased to maintain the production schedule. This assumes a 1% per year declining availability from 90% down to 85%.

Railveyor will primarily be used for haulage of ore material from stockpiles near the pits to the crusher feeding both the heap-leach pad and the mill.

Comminution

Crushers and Mills

Summary:

Heap-Leach Crushing Plant and Agglomeration
The DeLamar heap-leach crushing plant will comprise three stages of crushing, starting with a gyratory crusher for primary crushing, followed by a standard cone crusher for secondary crushing, and finally, two short-head cone crushers for tertiary crushing.

A specialized ROM conveyance system (“Railveyor”) will primarily deliver ROM to the primary crusher dump pocket. The crushed product will drop to the primary crusher product surge bin, which is equipped with an apron feeder that will deliver the ore to the primary discharge conveyor and on to a diverter cart. The diverter cart will allow primary crushed oxide and mixed ore to be routed to the oxide coarse-ore stockpile via a dedicated oxide ore stockpile feed conveyor, or non-oxide ore to be routed to the non-oxide ore stockpile via a separate, non-oxide ore stockpile feed conveyor.

Three apron feeders, two operating and one standby, will reclaim ore from the heap-leach coarse-ore stockpile and load it to the secondary screen feed conveyor. The secondary screen will separate +32 millimeter (1.25-inch) material and feed it to the secondary crusher. The screen undersize drops to a transfer conveyor and joins the secondary crusher product to the tertiary crusher feed bin.

From the tertiary crusher feed bin, the material is split between two tertiary screens with an aperture of 21 millimeters (0.82-inch). The oversize is fed to the tertiary crushers, whose products are recycled back to the tertiary crusher feed bin and on to the tertiary screens. The undersize of the tertiary screen is the final product of the crushing plant and has an estimated size of 80% finer than 12.7 millimeters (0.5-inch).

The crushing plant product is discharged to the crushing circuit product transfer conveyor where lime is added from a lime silo. The ore is then transferred to the stacking system feed conveyor or, alternatively, to the agglomeration feed conveyor, via a diverter cart.

Ore agglomeration will be achieved mainly at the transfer points of the grasshopper conveying system. Moisture will be supplied to the process by adding fresh water to the ore on the stacking system feed conveyor. For about 45% of the DeLamar oxide ore, agglomeration will be performed in an agglomeration drum using raw water or barren solution and cement, which will be added to the ore on the crushing circuit product transfer conveyor.

Milling Operations
Primary crushing of non-oxide ore will be performed in the same gyratory crusher as the heap-leach operation. Coarse ore will be retrieved and sent to a separate non-oxide coarse ore stockpile, from which ore is reclaimed by two reclaim feeders, and transferred to the SAG mill feed conveyor.

The grinding circuit comprises a SAG mill and a ball mill. The SAG mill will operate in a closed circuit with a vibrating screen. The oversize of the screen will be conveyed back to the SAG mill via the screen oversize conveyors and SAG mill feed conveyor. The undersize slurry will flow into the ball mill cyclone feed pump box as fresh feed to the ball mill circuit.

The ball mill will operate in a closed circuit with the primary hydrocyclone cluster, which sends the underflow back to the ball mill and the overflow to the flotation circuit via the trash screen. The target grind for the ball mill circuit is 80% finer than 150 microns.

Regrinding
The combined flotation concentrate will proceed to the regrind circuit, which consists of an ISAMill and a regrind cyclone cluster. The concentrate will enter the circuit through the regrind cyclone feed tank and will then be pumped to the regrind cyclone cluster. The underflow of the regrind cyclones will be fed by gravity to the ISAMill, which operates in open circuit. The overflow of the regrind cyclones and the product of the ISAMill both report to the pre-leach thickener, which will thicken the leach feed to 50% solids. The target grind of the leach feed is 80% finer than 20 microns. The pre-leach thickener overflow will be pumped to the process water tank.

Processing

• Smelting
• Crush-and-stack plant
• Flotation
• Heap leach
• Concentrate leach
• Agitated tank (VAT) leaching
• Counter current decantation (CCD)
• Merrill–Crowe
• Cyanide (reagent)

Summary:

The proposed process facilities for the DeLamar project comprise a heap-leach operation to process oxide and mixed ores, and a mill to process non-oxide ore. The heap-leach operation will have a nominal capacity of 35,000 tonnes per day while the mill will have a nominal capacity of 6,000 tonnes per day.

The heap-leach operation will employ a conventional heap-leach process, which will include three-stage crushing, agglomeration, and stacking on multi-lift dedicated leach pads. The mill process will include primary crushing, semi-autogenous (“SAG”) milling, ball milling, flotation, very fine grinding of flotation concentrates, cyanide leaching of the concentrates, and counter-current decantation (“CCD”). Pregnant leach liquors from both heap-leach and mill operations will be processed by common Merrill-Crowe and refinery facilities, to precipitate gold and silver from solution and smelt the precipitate to produce doré bullions.

The process facilities for the DeLamar project will be developed to accommodate the mining sequences of the Florida Mountain and DeLamar deposits. The LOM average head grades to the heap-leach operations are estimated to be 0.40g Au/t and 17.3g Ag/t.

The expected LOM average grades for the milling operations are 0.61g Au/t and 40.91g Ag/t. The mine schedule indicates that the heap leach will operate throughout the mine life, receiving ore initially from Florida Mountain, lasting though Year 7. DeLamar ore deliveries will start in Year 2 and continue through Year 17. The mill will start receiving non-oxide ore from both Florida Mountain and DeLamar in Year 3 and will continue until Year 17.

Heap Leach Operation
The final crusher or agglomerator product reports to the stacking system feed conveyor that feeds the first of the grasshopper conveyors. The initial stacking system will comprise 20 grasshopper conveyors, and an index feed conveyor and a horizontal index feed conveyor that feeds the heap- leach stacker conveyor.

The heap-leach pad will be a dedicated pad, which will be built in stages as mining progresses. The heap leaching facility will consist of two dedicated heap-leach pads, namely the Jacob’s Ridge leach pad and the Valley leach pad. Each leach pad will have its own pregnant leach solution (“PLS”) pond. The PLS pond at the Jacob’s Ridge leach pad will be sized to contain the operating volume, the drain down volume, and a 100-year 24-hour precipitation event, plus freeboard.

After stacking, pipe headers and drip irrigation lines will be added to the heap surface. Sodium cyanide solution will be applied to the heap surface via the header/drip system at a proposed application rate of 6.10 L/hr/m2 for the preliminary leach cycle of 120 days. The cyanide solution, applied at a nominal flow rate of 2,119 cubic meters per hour (9,329.7 gpm) to the heap surface, will percolate though the heap until it reaches the impervious leach pad liner at the bottom of the heap. The PLS will flow by gravity to the collection point of the leach pad and on to the pregnant solution pond for each leach pad. From the pregnant ponds, the PLS will be pumped to the clarifier filter feed tank in the Merrill-Crowe plant.

There are three solution ponds and all will be constructed in Phase 1. One of the solution ponds will be located at the north end of the Jacob’s Ridge heap and two ponds will be located at the north (lower) end of the valley heap. The pond at Jacobs Ridge is sized to contain an operating volume of 15,140 cubic meters (4,000,000 gallons) of pregnant solution storage, plus 100% of a 100- year, 24-hour precipitation event on the ridge portion of the heap, a volume of 24,000 cubic meters (6,342,400 gallons), plus a draindown volume of 24,224 cubic meters (6,400,000 gallons), plus the volume of 0.6 meters (2.0 feet) of freeboard, 7,066 cubic meters (1,867,000 gallons). As dimensioned, the overall volume of the Jacobs Ridge pond is 71,642 cubic meters (18,928,000 gallons).

Milling Operations
Ground ore will first be conditioned with potassium amyl xanthate (“PAX”), ethyl sec-butyl dithiophosphate (“Aerofloat 208”) and frother (“MIBC”) in an agitated tank for 15 minutes at 30% solids. Sodium metasilicate may also be added as a dispersant with high-clay ores. Once conditioned, the slurry flows by gravity to the rougher flotation (four cells) and rougher scavenger flotation (three cells) banks. Additional flotation reagents will be introduced to the slurry between the rougher and rougher scavenger banks. The combined rougher and rougher scavenger residence time is 45 minutes, to produce a combined flotation concentrate at an estimated mass pull of 10% for DeLamar ores and 5% for Florida Mountain ores.

The concentrate leaching circuit comprises six leach tanks operating in series followed by a CCD system. The leach tanks are designed to provide a residence time of four hours each, for a total leach time of 24 hours. Milk-of-lime (“MOL”) is added to slurry at the pre-leach thickener feed while sodium cyanide is added to the leach feed splitter box with stage addition of either into the leach tanks as required. Air is introduced below the agitators of each leach tank, supplied by one leach air blower.

The final leach residue will be pumped to the CCD circuit, which starts with a post-leach thickener and a series of four CCD cyclone clusters, which are supported by four agitated CCD mix tanks and four pumps (one operating per cluster). The cyclone clusters in series serve the same purpose as thickeners in series, with the post-leach thickener serving in the position of the first CCD stage. Overflow from the post-leach thickener is clarified in a thickener clarifier before being pumped to the Merrill-Crowe plant.

The PLS reporting to the pregnant solution pond and, starting year 3, solution from the CCD circuit pregnant solution clarifier will be pumped to the clarifier filter feed tank at the Merrill-Crowe plant. Solution clarification will be performed by three clarifying filters arranged to operate in parallel, with two operating and one on standby. The filters will have been precoated with diatomaceous earth (“DE”) to aid filtration. The solution may be infused with DE as body feed when required. The clarified solution then proceeds to the deaeration tower where it will be introduced into an evacuated chamber to remove as much dissolved oxygen as possible. After deaeration, powdered zinc, cyanide, and lead nitrate will be added to the solution to initiate an exchange redox reaction where zinc metal loses electrons to gold and silver, thereby reducing gold and silver to their metallic state and oxidizing zinc to form cyano complexes in solution.

The mixture will then be pumped to three recessed plate and frame filters operating in parallel, two operating and one standby. Precipitation of gold and silver by the exchange reaction continues as the solution makes its way to the Merrill-Crowe precipitate filters and reaches completion inside the filters. The filtrate solutions, stripped of values, will report to the barren solution tank. Additional cyanide and caustic may be introduced into the barren solution tank before it is recycled to the heap and to the leaching tanks and CCD circuit when the mill is operating.

Gold and silver precipitates collected by the filter presses will be dried in a retort to remove moisture and mercury before they are fluxed and smelted in an induction melting furnace. At the end of smelting, molten metal is poured into bullion molds to produce the final plant product, doré bars, which are packed for shipment.

The slag, which is poured first into a slag pot, will be weighed, sampled and stored for further processing if required, or transferred to the heap or fed to the ball mill when the mill is operating.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Chief Operating Officer	Tim Arnold		Dec 19, 2023
Consultant - Mining & Costs	Tom Dyer		Jan 24, 2022
Consultant - Recovery Methods & Costs	Benjamin Bermudez		Jan 24, 2022
Engineering Manager	Mike Spicher		Dec 19, 2023
Site Operations Manager	Matthew Mock		Dec 19, 2023