Mineralization at Tahuehueto is classified as intrusion related epithermal low sulfidation polymetallic AgAu style (Corbett, 2007), with Au and Ag accompanied by Cu, Pb, and Zn mineralization. These types of deposits are interpreted to have been derived from porphyry intrusion source rocks at depth.

Mineralization at Tahuehueto occurs as polymetallic epithermal veins with multiple mineralizing events overprinted on one another in the same vein structure. The primary host rock is andesite of the lower volcanic series, but in at least one case, the hydrothermal system penetrated felsic ignimbrite of the upper volcanic series. Styles of mineralization identified by Corbett (2007) include:
-Initial pervasive propylitic-potassic alteration with local specular hematite develops as intrusion-related alteration.
-Early chalcopyrite-pyrite mineralization, locally with quartz-barite typically forms early and at deeper crustal levels in polymetallic Ag-Au vein systems.
-Polymetallic Ag-Au mineralization comprising pyrite-galena-sphalerite ± chalcopyrite ± chalcopyrite ±Ag sulfosalts ± barite represents the volumetrically most apparent mineralization and displays pronounced vertical variation discerned as changes in the sphalerite color from dark brown Fe-rich high temperature sphalerite formed early and at depth to red, yellow and less commonly white sphalerite as the Fe-poor low temperature end member that typically develops at higher crustal levels and as a later stage. Much of this mineralization occurs as sulfide lodes or as breccia infill. Bulk lower grade mineralization occurs as fine grained Au and Ag sulfosalts deposited within base metal sulfides as part of the main polymetallic mineralization, rising to higher grade Ag with increased base metal contents. These events evolve to mineralization with a more epithermal character and locally higher Au-Ag grades at later stages where base metal sulfides are overprinted by Ag-rich tetrahedrite (freibergite).
-Highest Ag-Au grades locally occur in the absence of Cu-Pb-Zn in ores described as the epithermal end member of polymetallic Ag-Au mineralization which is strongly structurally controlled. High grade Ag may occur as freibergite with celadonite in combination with white sphalerite and dark chlorite commonly with later stage opalchalcedony. Semi-massive to banded chlorite locally occurs with celadonite-pyrite-opal and displays elevated Au with significantly lower Ag: Au ratios. Hypogene hematite occurs with banded quartz as an epithermal assemblage which accounts for elevated Au grades overprinting earlier sulfiderich mineralization.

Breccias are an integral part of the Tahuehueto hydrothermal system and display several genetic styles. Corbett (2007) notes that many of the sulfide-mineralized zones display sulfide transport textures; typical of fluidized breccias. Milled breccias are those in which the clasts have undergone significant working while being transported from deeper to elevated crustal settings. These breccias typically contain rounded clasts in a matrix of milled rock flour which has undergone hydrothermal alteration. Expansion breccias, in which the fragments have been moved apart and filled in with carbonate or quartz in a jigsaw pattern, are typical in dilational structural settings. Magmatic hydrothermal breccias typically occur in near porphyry environments and contain clasts of porphyry intrusions and alteration in a milled matrix. Shingle breccias with elongate, parallel shingle-like fragments, are thought to have been formed by collapse following the explosive escape of volatiles from an underlying magma chamber.

The uppermost portions of the mineralized structures are oxidized. In the oxide zone, mineralization consists of malachite, azurite, chalcocite, covellite, limonite, and hematite. Malachite overprints tetrahedrite, and chalcocite and covellite form coatings on sphalerite. The depth of the oxide-sulfide interface varies considerably, but is generally less than 100m.

Sulfide mineralization lies below the oxidized zone and consists of sphalerite, galena, chalcopyrite, tennantite, tetrahedrite, and probably electrum. Gangue minerals are quartz, pyrite, chlorite, sericite, and calcite. Locally a light green phyllosilicate mineral interpreted to be celadonite (Loucks, et al 1988) forms as gangue and is closely associated with high-grade gold and silver mineralization.

The geometry and orientation of the Tahuehueto mineralized veins are conducive to sublevel stoping. The Perdido, Creston, and Rey primary development intersects the veins near the midpoint of the target mineralization allowing for bottom-up and top-down sequencing; the Santiago and Cinco veins are developed as top-down mining only. A 3-meter pillar every three sublevels may be utilized to maintain rock integrity and proper backfill sequencing.

Altaley has developed approximately 1,200 meters horizontal and 75 meters of vertical development off the 20 Level and 350 meters plus several ore cuts off the 12 Level. All development completed to date accesses the Perdido and Creston veins in preparation of being in a position to produce ore following commissioning of the mill.

Overhand Cut and Fill mining method with conventional drilling, blasting, mucking and hauling, scaling and ground support installation and backfilling with unconsolidated, mined waste materials was evaluated as a trade-off study. The Cut and Fill results improved metal extraction; however, it was determined that excessive development was required accessing the levels off the decline resulting in reduced economics.

This crushing circuit is scheduled to operate 12 hours per day and will receive ore from the mine in 20 t capacity dump trucks discharged to the coarse ore feed bin with a capacity of 80 t. The feed bin will have a 46 cm grizzly. The oversize ore material will be reduced with the use of pneumatic rock breaker.

The ore from the coarse ore bin, reports to the primary jaw crusher by an apron feeder, and then reports to a vibratory grizzly pan feeder. Pan feeder undersize reports to the primary crusher product conveyor (CV-01). Pan feeder oversize reports to the Primary Jaw Crusher (JC-01). The Primary Jaw Crusher product reports to the Primary Crusher Conveyor.

The Primary Crusher Conveyor discharges to the Secondary Crusher Vibratory Screen (VS-01), The Vibratory Screen undersize reports to the Final Product Conveyor (CV-02). The Vibratory Screen Oversize reports to the Secondary Crusher Feed Conveyor (CV-03) which in turn discharges to the Secondary Crusher Feed Surge Bin (SB-01). Material from the Surge Bin reports to the Secondary Cone Crusher with the Cone Crusher product reporting to the Primary Crusher Product Conveyor (CV-01) where it is added to the product from the Primary Jaw Crusher. The mixed ore is subsequently processed through the Secondary Vibratory Screen with the screen undersize reporting to the Final Product Conveyor (CV-02). The final Product Conveyor reports to the Fine Ore Bin (FB-01).

Fine ore from the Fine Ore Bin discharges to the Ball Mill Feed Conveyor (CV-04) and feed into the Primary Ball Mill (BM-01). Water is mixed with the ore to maintain a slurry density of 70 percent solids (wt:wt) in the mill. The Ball Mill discharges to Ball Mill Discharge Trommel when the oversize is returned to the mill and undersize passes to the Cyclone Pump Box (PB-01). Water is added to the pumpbox to dilute the slurry to 30 percent solids (wt:wt) before being pumped to the Cyclones (CY-01) via one of the two Cyclone Feed Pumps (PP0-01A/B). Cyclone underflow reports back to the ball mill feed with the cyclone overflow reporting to the Pb Flotation Conditioning Tank (TK-01).

The ore slurry is conditioned with reagents in the Pb Flotation Conditioning Tank (TK-01), where the ore is conditioned with reagents as required before reporting to the Pb flotation cells. Conditioned slurry reports to the first set of flotation cells known as the Primary PB Roughers Flotations Cells. Concentrate from the Primary Pb Roughers reports to the final concentrate pumpbox (PB-04) or the Pb 1st/2nd Cleaner Flotation Cells depending on grade. Primary Pb Flotation Tailings report to the 1st Pb Rougher Flotation Cells. Concentrate from the 1st Pb Rougher Flotation Cells reports back to the Primary Pb Floatation Cells. Tailings from the 1st Pb Rougher Flotation Cells reports to the 2nd Pb Rougher Flotation Cells. Concentrate from the 2nd Pb Rougher Flotation Cells report to the 1st Pb Rougher Pump Box with the 2nd Pb rougher Flotation Cell tailings reporting to the Zn Flotation Conditioning Tank.

Concentrates from the 1st/2nd Pb Cleaner Flotation Cells report to ........