The Pirquitas deposit is an example of the Ag Sn sub-group of the epithermal class of mineral deposits (Panteleyev, 1996). Also known as Bolivian-type polymetallic deposits, examples of this deposit type are numerous in the Bolivian Silver -Tin Belt that extends between the San Rafael Sn(-Cu) deposit in southern Peru and the Pirquitas deposit in northwestern Argentina.

Bolivian-type Ag-Sn deposits generally consist of sulphide and quartz-sulphide vein systems typically containing cassiterite and a diverse suite of base and trace metals, including Ag in a complex assemblage of sulphide and sulfosalt minerals. The vein systems are generally spatially and likely genetically associated with epizonal (subvolcanic) quartz-bearing peraluminous intrusions one to two kilometres in diameter, although the mineralization may be entirely hosted by the country rocks into which the intrusive stocks were emplaced.

The suite of principal and subordinate ore minerals that characterize this deposit type includes, but is not limited to, pyrite, cassiterite, pyrrhotite, marcasite;,sphalerite, galena, chalcopyrite, stannite, arsenopyrite, tetrahedrite, scheelite, wolframite, andorite, jamesonite, boulangerite, ruby silver (pyrargyrite), stibnite, bismuthinite, native bismuth, molybdenite, argentite, gold and a variety of complex sulfosalt minerals. Metal zoning from depth to surface and from centers outward shows: Sn + W, Cu + Zn, Pb + Zn, Pb + Ag, and Ag ± Au; commonly there ........

Mining of the San Miguel open pit ceased in January 2017. Previously, the Pirquitas mine used a standard open pit mining method and conventional drilling and blasting activities with a pre-split to ensure stable wall rock conditions. RC grade control drilling was used in the pit to define the structurally controlled vein and breccia hosted ore zones. The depth and relatively lower grade of the ore body made the Mineral Reserves and Mineral Resources at the Pirquitas mine amenable for open pit mining.

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