The mineral deposits at San Bartolomé are alluvial and colluvial, surficial accumulations of silver- and tin-bearing unconsolidated material, which were derived from erosion of Cerro Rico, a prominent +4,700 meter elevation mountain, and accumulated down-slope filling depressions, gullies and low-gradient areas. Locally they are called “pallacos” which also includes reworked Sn-bearing gravel deposits called “sucus” and “troceras”. Asiento and Tatasi-Portugalete are man-made dumps (“desmontes” or “stockpiles”) adjacent to underground mine portals of ancient and current mines. Only Cachi Laguna is an in situ silver and gold mineral deposit and is high sulfidation, epithermal in nature.

San Bartolomé
The mineral deposits at Cerro Rico are the source of the San Bartolomé pallacos and are high sulfidation epithermal in character, composed of veins, stockworks, hydrothermal breccias and irregular bodies, hosted in a very altered resurgent dome of dacitic- to rhyodacitic-composition porphyritic intrusion emplaced in Middle Miocene time (approx. 14 mya).

The pallacos were derived from the erosion of the Cerro Rico hydrothermal ore deposit and were emplaced around the mountain crest by recent geologic processes. These deposits consist of an unsorted mixture of cobbles and boulders in a sandy clay matrix, accumulated down slope by colluvial and alluvial processes, filling depressions, gullies and low-gradient areas. They cover an area of over 5 km2 in size. True thicknesses of the pallacos range from <1 m to nearly 75 m. The deposits have been grouped into three areas named Antuco (within the greater Diablo area), Huacajchi and Santa Rita. The primary rock source of silver content for pallacos is the mineralized, silicified wall rock adjacent to the veins and disseminations of Cerro Rico. Rock clasts are highly oxidized, variably silicified and mineralized with disseminated native silver, sulfosalts of silver, argentite, jarosite and psilomelane (Mn oxide). Pallacos grade from predominantly coarse, broken rock on the upper slopes into a mixture of coarse rock fragments in a sandy clay matrix down slope to more fine-grained material further downslope. The surface area of the current mineral resources is approximately 337 hectares.

The massive mineralizing system centered on Cerro Rico resulted in, by all accounts, the largest single concentration of silver known and produced the textbook Bolivian Tin Belt sub-volcanic dome-hosted silver-tin vein deposit.

Although vein mineralization undoubtedly contributes to the silver content of the pallaco deposits locally, it is the disseminated mineralization within wall rock between and adjacent to the vein system which controls the overall grade of the clasts within the pallaco deposits. The disseminated silver mineralization with the silicified wall rock, particularly the silicified rhyodacite, is preserved in the pallaco clasts. It is this silver mineralization which is primarily recovered by the San Bartolomé Project.

Vein mineralization is zoned vertically from a high-temperature core of quartz-pyritecassiterite-arsenopyrite-bismuthinite at depth through an intermediate zone of quartz-stannite-sphalerite-chalcopyrite-tetrahedrite to an upper zone of ruby silvernative silver-cassiterite-jamesonite-boulangerite. Silver-bearing minerals are zoned from tetrahedrite-andorite at depth upward into argentite-pyrargyrite-native silver in the upper levels of the system.

Vein mineralogical zoning is less pronounced horizontally. Sphalerite, galena and pyrite are reported to increase towards the margins of the intermediate zone.

Silver mineralization post-dates tin, and becomes enriched upward in the system. Both the tin and silver disseminated in the quartz-tourmaline and vuggy-silica alteration were deposited contemporaneously with similar vein mineralization. The intensity of the disseminated mineralization increases with increasing proximity to the sheeted-vein zone. Above the 4,400 m elevation, the mineralization is strongly oxidized with less than one percent relic primary sulfide consisting predominantly of pyrite.

Silver occurs as native silver, chlorargyrite, pyargyrite, argentite, argentojarosite, argentianpsilomelane, and silver-bearing iron oxides and hydroxides. On average about 70% of the contained silver is recoverable through cyanide leaching. The other 30% is contained in refractory iron compounds or is silica encapsulated.

Tin occurs as cassiterite in very-fine grained, hypogene intergrowths with quartz and as powdery aggregates likely derived from oxidization of tin sulfide (stannite) and sulfosalts (teallite and franckeite). Quartz is the primary gangue mineral (+90%) along with traces of hematite, magnetite, goethite, zircon and ilmenite. Barite occurs in abundance locally (Huacajchi).

Disseminated silver and tin mineralization in vuggy-silica alteration is the most important ore-source rock within the pallaco/escombreras deposits of the San Bartolomé Project.

El Asiento Dumps
The source of the El Asiento dumps is the primary, hypogene polymetallic deposits hosted in folded and faulted sediments, intruded by dikes related to subvolcanic, dacitic, porphyry stocks. The sedimentary and intrusive rocks contain veins and occasional polymetallic stockworks (Ag-Zn-Pb). Some Ag-bearing, rosario-type veins and veinlets are documented, with tetrahedrite and galena mineralization. Years of operation generated dumps with exploitable mineral content within oxidized material. Because of oxidation, historic and current miners are not able to utilize the common flotation plants located in the region (which are designed for sulfide material). Metallurgically, these dumps are much more amenable to the relatively unique (in Bolivia) NaCN leaching circuit at San Bartolomé. The surface area encompassing the El Asiento dumps is approximately 100 hectares in size.

Tatasi-Portugalete Dumps
The in situ source of the Tatasi-Portugalete dumps are high sulfidation, epithermal (hydrothermal) polymetallic deposits (Ag-Zn-Pb) related to volcanic domes and dikes intruded into a shale and quartz sandstone sequence, along with pyroclastic and lava flows. This volcanic-sedimentary sequence developed a radial fracture system, with hydrothermal alteration, containing veins, veinlets, stockworks and disseminations. The primary deposit is zoned vertically, with silver-rich upper levels grading into zinc-rich deeper levels. Years of operation generated dumps with exploitable mineral content within oxidized material. Because of oxidation, historic and current miners are not able to utilize the common flotation plants located in the region (which are designed for sulfide material). Metallurgically, these dumps are much more amenable to the NaCN leaching circuit at San Bartolomé. The surface area encompassing the Tatasi-Portugalete dumps is approximately 320 hectares in size.

Cachi Laguna In Situ Material
The Cachi Laguna area, approximately 150 hectares in size, consists of a central, quartz latite porphyry dome, a massive rock as seen in drilling cores, while its surrounding area is characterized by lava and pyroclastic flows. An irregular breccia-like ring separates the dome from the flows sequence. Faults and other structures, of mainly NW-SE and NE-SW orientations, are common throughout the dome and were important for deposit emplacement in some cases, while in others lithology was the main control.

Mineralized bodies show three main styles: vuggy silica (Claudia Eugenia and Corona Bajo areas), hydrothermal breccias (scattered in all zones and related to the other types), and sulfidic inter-mineral breccias (Brecha Norte and Corona Alto). Twelve mineralized sectors have been discovered; all vertically elongated. Mineralized zones of stockworks and veins are also present, as well as of phreatomagmatic breccias.

Ore is mined from the Company’s permitted mineral reserve areas:
The San Bartolomé mine (“pallacos”).
Dump areas at Tatasi-Portugalete and El Asiento.

The project utilizes conventional surface mining methods to extract colluvial, and alluvial materials mine dumps, oxide and sulfide tailings and other materials named pallacos and sucus and troceras (collectively, the “pallacos”), which have been identified in the Huacajchi, Santa Rita, Diablo (Norte and Sureste areas – now referred to as Antuco) - Pallacos Areas.

An exclusive mineral purchase contract is in place between Manquiri and RALP Compañía Minera, S.R.L., a private, Bolivian mining company (“RALP”). The contractual rights held by Manquiri are for processing of 108,000 tonnes of silver- and gold-bearing material being mined by RALP.

The current mine plan is designed with 5 m benches and 2 m berms. Additional 5 m wide safety berms were included in the design when the slope height exceeds 25 m.

Dump areas at Tatasi-Portugalete and El Asiento will be fully reclaimed in 2 m slices in a top-down sequence. If internal operational slopes are required, the angle of repose of 37° will be considered.

The mining strategy adopted by Manquiri is a mixed between an owner operation and contracted:
• In the pallacos areas Manquiri operates the loading with owned excavators of 2.4 / 2.6 m3 and auxiliary operations (bulldozers and motor graders) and the hauling of the ore to the plant is contracted with 24 tonnes conventional trucks operated by local “cooperativas”. The re-handling at the plant area is owner operated with front-end-loaders of 3.4 / 4.2 m3 and 24 tonnes trucks.
• All mining activities at Cachi Laguna are contracted, except for the drilling.
• At the mining dumps at Tatasi-Portugalete and El Asiento, the mining activities are fully contracted.

There are two separate ore types that are handled in the washing and crushing circuit. One is called whole ore and the other is called screen ore. Each ore type has its own crushing process circuit. The whole ore is either direct dumped by truck from the mine into a feed bin or recovered from the stockpile by a front-end loader and delivered to a feed bin.

The whole ore is fed by an apron feeder that delivers the ore to a jaw crusher. The ore is crushed in the jaw crusher to no more than 76 mm. The crushed ore is delivered by conveyor to the crushed ore stockpile. The crushed ore stockpile has a capacity of approximately 5,200 tonnes live storage (i.e., immediately available for use in the downstream processes).

The screen ore is fed by an apron feeder to an ore-sizer which reduces the larger particles to less than 10 cm. The sizer is a dentate roller crusher. The sized material is delivered to a washing system consisting of a rotary drum washer and a triple deck shaker screen. The wash water and fine particles passing through the bottom deck (8 mesh screen) are pumped to a tailings disposal facility. The top deck oversize material normally coarser than 50 mm is fed into a 120 cm short head cone crusher. The crushed product is combined with the middle deck oversize material (>2.4 mm to < 50 mm size) and conveyed to the crushed ore stockpile which provides feed for the grinding circuit.

The crushed ore is reclaimed from the crushed ore stockpile using a front-end loader. The loader feeds a bin that discharges into a conveying system then the ore is fed to a Semi-Autogenous Grinding (SAG) mill. As the ore is discharged from the conveyor into the SAG mill, water and lime slurry (pH modifier) are added. New grinding balls are added to replenish the ball charge of the mill as the grinding balls in the mill are consumed. The slurry discharging from the SAG mill flows onto a trommel screen. The screen removes the oversize material, which is returned to the SAG mill. The crushed ore is ground in the SAG mill to approximately 48 mesh at which size the ore is reduced sufficiently in size to where the particles can be efficiently broken in the downstream ball mill.

The plant was designed to operate 24 hours a day, 365 days a year with 92% availability. At full, design capacity, the plant can process up to 4,800 tonnes/day (1.5-1.6 million tonnes per year). In addition to silver, smaller quantities of gold are also recovered from the leaching of the oxidized, silver-rich ores. Transitional and/or sulfidic material does not exist in the pallaco mineral resources but has been identified in some of the historical purchased materials.

The silver is leached using a sodium cyanide (NaCN) solution and the plant is designed to recover approximately 78.0% of the silver from the ore, although metallurgical recovery will vary with different ore types. Thus, the final valuable product from the plant is 99.95% silver, but is called doré.

Cyclone overflow slurry produced by the grinding circuit is directed over a trash screen and then pumped to the cyanide leach circuit.

Manquiri test work in 2019, yielded improvements in meta ........