The deposit at Amancaya is an epithermal gold and silver deposit, hosted in a steeply dipping structurally controlled quartz vein. Gold mineralization comprises disseminations of native gold and silver, electrum, silver sulphosalts, and accessory sphalerite, galena, chalcopyrite, and pyrite occurring with quartz, adularia, carbonates, clay minerals, limonite, and manganese oxides. These minerals were deposited from boiling of dilute saline fluids circulating in a hydrothermal system driven by the Eocene to Paleocene magmatism. The hydrothermal vein systems are considered a low sulphidation type based on their metal content and the volcanotectonic setting.

The most relevant mineralization from an exploratory point of view corresponds to the low sulphidation epithermal veins rich in gold and silver. These structures are distributed to the east of the La Peineta Fault System, along a north-south corridor of approximately two kilometres by eight kilometres (Central Veta Sector and Rosario del Llano Mine). They are mostly housed in the basal units of Paleocene (Chile-Alemania Formation, e.g., Amancaya Breccia).

In the Cerro Morros Blancos sector towards the southeast of the Central Vein, there is an area of advanced argillic type alteration that affects the basal units of the Paleocene. This sector is characterized by the presence of fault breccias with alunite and kaolinite, and subhorizontal silicified layers.

To the west of the Peineta Fault system there is mineralization of which the most important is the gold-copper veins of the Amancaya West sector. The veins strike north-south, 020° and 330° possibly associated with a porphyritic system of the Upper Cretaceous. In this sector, moreover, manifestations of IOCG mineralization linked to the Fm. La Negra, have been found.

Finally, thick quartz epithermal veins with iron and copper oxides are recognized in the sector Northwest sector, embedded in Devonian and Triassic units (Las Tórtolas formation and Agua Verde Granodiorite).

All of the veins that occur at Amancaya can be subdivided into two groups according to host units.
• Veins hosted in dacite-andesite domes (Central, Griega, Inesperada, and Cerro Amarillo).
• Veins hosted by breccias, tuffs, and volcanoclastic rocks (Rosario del Llano, Janita, Rosa, Nueva, and Julia etc.).

The main veins have been grouped within the Southern Block (Veta Central, Veta Griega, Veta Julia), and North Block (Veta Janita, Veta Nueva, Veta Rosa, Veta Laureana, Rosario del Llano, etc.).

The Amancaya Mine underground Mineral Reserves were estimated based on stope designs applied against the Mineral Resource block models for the Central Vein deposit. Planned and unplanned dilution are included in the stope shapes which have been designed for a sub-level stoping mining method.

The sub-level open stoping (SLOS) mining methods employed are similar to those used at the Guanaco Mine. The Amancaya orebody is generally thinner than Guanaco resulting in the use of split-blasting to minimize dilution during drift development. Split blasting involves the separate blasting of ore and waste in the drift face. [p. 285]

Similar to Guanaco, Amancaya will use the vertical crater retreat (VCR) to connect the upper and lower drifts and create and open face for long hole blasting. [p. 285]

Amancaya will utilize the same underground mining equipment fleet from Guanaco. [p. 309]

With the acquisition and start of mining at Amancaya, commissioning of a 1,500 tpd agitated leach milling circuit commenced in March 2017, expected to be fully operational by July 2017. [06/16/2017 TR, p. 311]

2018 - First full year operating the new agitation leaching in plant. The Amancaya ore is being trucked to the new plant at Guanaco for processing.

The new construction includes:
• Reversing conveyor to feed either the heap leach operation or the milling circuit
• Covered stockpile
• Single stage ball milling circuit operated in closed circuit with hydro-cyclones
• Pre-leach thickener
• Three-stage agitated leach circuit
• Three-stage counter-current-decantation (CCD) wash circuit
• Filter feed tank and plate and frame pressure filters to recover solution and produce filtered tailings
• Loading with front end loader and truck haulage to dry tailings deposit
• Dry tailings deposit
• Refurbished Merrill-Crowe ........