The San Gonzalo Vein is located approximately 1.4 km northeast of the eastern modelled extent of the Avino Vein. The San Gonzalo Vein system constitutes a strongly developed vein system over 25 m wide, trending 300° to 325°/80° northeast to 77° south. It is characterized by banded textures and openspace filling. The main vein has an average width of 2 m, but the silica-pyrite or iron oxide-sericite alteration with additional stock working extends across 300 m, south of the main San Gonzalo Vein to the Los Angeles vein.

The San Gonzalo is a typical narrow vein precious metal deposit with some erratic values and extends approximately 2 km to the northwest to the Santa Ana-Malinche area (Gunning 2009).

The Cerro San Jose-La Estella-San Gonzalo Cerro San Jose represents a distinct hydrothermal centre with similar characteristics to the Avino system which include the following (Paulter 2006):
• occur on a topographic high
• strong to intense silicification and brecciation
• easterly trending stockwork system similar to the trend of the Avino Vein
• similar temperatures of formation to Avino
• presence of an intersecting northwesterly trending vein system (la Estella at San Jose and San Juventino at Avino)
• emplacement along a northerly trending, deep crustal fault zone (defined by the Aguila Mexicana Vein at Cerro San Jose and the felsic dyke at Avino).

Cut-and-fill and shrinkage stoping methods are being used.

Access to the underground mining on the San Gonzalo Vein is via a 4 m by 4 m decline developed at - 12%. Ground conditions are good. Ground support is mainly bolting as required.

San Gonzalo is using shrinkage mining for the narrower material, approximately 1.4 m in width and cut and fill mining for mineralized material wider than 2 m.

During shrinkage mining, miners use hand-held jacklegs and stopers to drill and blast in stopes. Material is drilled and blasted using jacklegs to breast horizontally, with two miners from two ends of the stope with several breasts worked on at once. After each blast the swell (approximately 40% of the broken material) is mucked from the extraction drift below to allow room for the miners to drill the next lift.

Materials and supplies are carried into the stopes by hand down a small raise equipped with steel ladders and a rope. Only 40% of the material is extracted during mining, with the remainder being extracted after all the mining has been completed, meaning more stopes are required in the development stage at one time to sustain production targets. Scoops are used to muck from the extraction drift below and trammed to a mineralized material pass.

Cut and fill mining is more mechanized, as access for scoops is maintained in the stopes from the main ramp by a smaller access attack decline/incline ramp. This access means less manhandling of materials and provides material on a steady basis from each lift while mining takes place. This method requires that waste fill be placed after each lift of material has been mined prior to mining the next lift. Stopers are used to drill vertical holes, with half the stope being blasted at once. A 2 yd. scoop is used in the stope to place waste and muck material. It is 1.2 m wide and requires 2.0 m wide to operate. No mill discharge is used for backfilling.

The mine is able to achieve a production rate of 230 t/d with three shrinkage stopes and one cut and fill stope being developed/mined at once plus two headings in mineralized material or the shrinkage undercut. The mine works 6 d/wk, or 26 d/mo. A mining contractor has been hired for material haulage.

The Avino Mill serves the Avino and San Gonzalo mines.

The process plant consists of crushing and grinding facilities, followed by a flotation process circuit to recover and upgrade silver and gold from the feed material. Common reagents were used within the flotation circuit. The flotation concentrate is thickened, filtered and sent to a concentrate stockpile for subsequent shipping to customers.