The Caylloma Mine is within the historical mining district of Caylloma, northwest of the Caylloma caldera complex and southwest of the Chonta caldera complex. Host rocks at the Caylloma Mine are volcanic in nature, belonging to the Tacaza Group. Mineralization is in the form of low to intermediate sulfidation epithermal vein systems.

Epithermal veins at the Caylloma Mine are characterized by minerals such as pyrite, sphalerite, galena, chalcopyrite, marcasite, native gold, stibnite, argentopyrite and silver-bearing sulfosalts (tetrahedrite, polybasite, pyrargyrite, stephanite, stromeyerite, jalpite, miargyrite and bournonite). These are accompanied by gangue minerals, such as quartz, rhodonite, rhodochrosite, johannsenite (manganese pyroxene) and calcite.

Mineralization vein systems occurs in steeply dipping ore shoots ranging up to several hundred meters (“m”) long with vertical extents of over 400 m. Veins range in thickness from a few centimeters (“cm”) to 20 m, averaging approximately 1.5 m for silver veins and 2.5 m for polymetallic veins.

The mining method applied in the exploitation of the two main veins (Animas and Bateas) is overhand cut-and-fill using either mechanized, semi-mechanized or conventional extraction methods. All mining is undertaken in a southwest to northeast direction following the strike of the veins. Production capacity at the mine is 1,430 tonnes per day (tpd) since the upgrade to the plant in March 2016 but has the potential of achieveing 1,500 tpd.

Mechanized mining utilizes a jumbo drill rig and scoop tram for loading. The ore haulage is performed by a combination of locomotives and trucks. Rock support is applied through rock bolts and shotcrete. The average mining width ranges between 3.5 m and 17 m. Mechanized mining is regarded as only being suitable for the Animas vein based on the geological structure and geotechnical studies. Approximately 90 percent of production comes from the Animas vein.

Semi-mechanized mining is performed using handheld drilling equipment (jacklegs) and scoops for loading. Ore haulage is performed by a combination of locomotives and dump trucks. Rock support is supplied using rock bolts installed using manual drilling and installation techniques. Semi-mechanized mining is applied to narrow veins with average widths between 0.8 m and 2.0 m.

Conventional mining is performed using handheld drilling equipment (jacklegs) and scrapers for loading. The ore haulage is done with trains and rail system and the support is applied with rock bolts in manual form. This system is applied in narrow veins with average widths between 0.5 m and 0.8 m.

The underground mine is operated by a mining contractor selected by Minera Bateas based on a competitive bidding process. The scope of work for the mining contractor generally includes mine decline and raise development, stope preparation development, stoping, backfilling, and all related services required for the operation of a 1,500 tpd narrow vein silver-gold-lead-zinc mine.

The Minera Bateas processing plant is a typical flotation operation and consists of five stages: crushing; milling; flotation; thickening and filtering and tailings disposal.

The Caylloma Mine concentrator plant resumed operations in September 2006, treating 600 tpd of polymetallic mineral. Capacity increased progressively, with the installation of a 1.8 m by 2.4 m ball mill in 2009 the plant reached a treatment capacity of 1,300 tpd, and with the installation of two Derrick Stack Sizer vibrating wet screens the plant achieved a treatment capacity of 1,500 tpd at the end of March 2016, although this has since been reduced to 1,430 tpd for the rest of 2016. The treatment process is differential flotation. Initially, two concentrates were obtained: lead-silver and zinc. From late 2009 to January of 2011, a copper-silver concentrate was also produced, but due to unfavorable commercial terms the production of copper concentrate was suspended and the copper circuit put on standb ........