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 is strongly telescoped, with early high temperature mineralization and alteration overprinted by intermediate temperature and then by younger epithermal mineralization and alteration assemblages. The multiple mineralizing events obscure vertical zonation patterns that are commonly found in other epithermal vein deposits.

Mineralized zones are characterized by pervasive silicification, quartz-filled expansion breccias, and sheeted veins. Multiple phases of mineralization produced several phases of silica, ranging from chalcedony to comb quartz (Corbett, 2007). The surface expression of known mineralization occurs over a vertical distance of at least 850m between Cinco de Mayo and Santiago. The El Creston mineralized zone has been developed by 10 levels over 490m vertical distance.

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 mine ........

The geometry and orientation of the Tahuehueto mineralized veins are conducive to sublevel stoping. The Perdido, Creston, and Rey primary development intersect 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.

The sublevel mining method exposes operators to the rock surface during the development of the sublevels. If the ground conditions deteriorate, then artificial support shall be installed to maintain integrity. Sublevels (nominally 3.5 m wide by 4 m high) are developed ........

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