The Avino Vein is 1.6 km long and 60 m wide on the surface. The Avino Vein is the most striking and important example of the epithermal mineralization of the district whose structures are normally weathered and leached in their upper section as a result of contact with atmospheric waters producing a band of oxide minerals and zones of supergene enrichment to a depth of about 70 m.

In the oxide portion of the Avino Vein, the common minerals encountered include hematite, limonite, anglesite and copper carbonate in white or green, somewhat chloritized, quartz zones. The common primary and secondary minerals encountered are argentite, bromargyrite, chalcopyrite, chalcocite, galena sphalerite, bornite, native silver, free gold, and native copper. Other minerals present in mineralized areas include quartz, pyrite, chlorite, barite, arsenopyrite, pyrrhotite and specularite.

Higher silver values are reported to decrease overall with depth, except at vein intersections and vein inflections, where higher values persist to depth. The same can be said for gold, although the higher values start just below the onset of silver mineralization, at or near the surface. In contrast, higher copper values coincide with vein intersections and may increase with depth. Sporadic, localized copper enrichment occurs toward the footwall contact and may represent a different phase of fluid emplacement. Despite the overall decrease in precious metal grade with depth, local increases in metal grades are apparent in the mine sampling and exploration drilling, possible reflecting changes in boiling level with pressure variations in the epithermal system.

The Avino Vein has been followed longitudinally for more than 1,300 m and vertically for more than 600 m. It strikes north 66° east with an east-west splay, and dips to the south and southeast at 60° to 70°. Steeply dipping, high grade zones within the vein and stock-work zones are frequently found in the upper part of the vein, as well as at its intersections with a number of lateral veins. An example of a higher- grade area of mineralization encountered with major lateral vein intersecting the Avino was the El Hundido, which exceeded 40 m in thickness. In the lower areas of the vein and mine, mineralized cross-veins, branch-veins, and stockwork zones have been found in the footwall at San Luis and at El Hundido, and are assumed to persist with depth.

The hanging wall of the Avino Vein is andesite, while the footwall is a monzonite intrusive with andesite sections. A post-mineralization fault parallel with the vein occurs in the hanging wall at a distance of several metres in the area of San Luis, while in the central part of El Hundido, this fault is located at the contact with the vein over a distance of about 300 m, up to the area of Santa Elena and San Antonio. From that point, and proceeding toward the El Chirumbo Mine, this fault cuts the vein between the face at San Carlos and the exposure at the underground ramp. The fault then enters the footwall where it remains until a point about 30 m east of the west face of the Chirumbo area, producing a downward displacement of the vein of between 50 to 100 m.

At Chirumbo, the fault largely replaces the vein due to strong leaching by post-mineralization circulating of water in the gouge. On the east face at Chirumbo, the fault again enters the hanging wall; in this zone the vein is composed of branches and stockwork and to the east of this point the fault crosses the vein numerous times.

The deposit is epithermal and made up of veins and dependent stockwork structures, mainly in the hanging wall and often associated with vein intersections. Four vein systems have been described which, in decreasing order of importance, are:

• system striking east-west, dipping south at 60° to 70°, including the Avino Vein and its possible extension in the Cerro de San Jose

• system striking north 60° to 70° west, dipping 60° to 80° southwest, comprising the following important veins: El Trompo, San Juventino, San Jorge, Platosa, Los Reyes, Potosina, El Fuerte, and Conejo

• system striking north 20° to 30° west, dipping between 60° to 80° to either the southwest or northeast, comprising the following significant veins: San Gonzalo, Aguila Mexicana, and La Calcita, as well as the Stockwork La Potosina, and the Stockwork El Fuerte

• systems striking north 60° to 80° east, dipping 60° to 80° southeast, comprising the following veins: Santiago, Retana, Nuestra Senora, and San Pedro and San Pablo.

Avino is currently mining on the Avino Vein using sublevel stoping and room and pillar mining methods. Levels are spaced 20 m apart and accessed via crosscuts from the main ramp. Access into the Avino Vein is through the ET Mine.

The room and pillar mining method is used on each sublevel to mine out each level to the extents of the mineralization. Long holes are then drilled between the sublevels to facilitate blasting of the mineralization between the sublevels. In 2020, Avino reported it will transition from development-style mining to full-scale production mining to feed all four circuits using the long hole retreat mining method, which is anticipated to incur lower mining costs.

The existing crushing plant was upgraded to accommodate the higher throughput. Mill feeds from different sources will be crushed separately, and the crushed materials will be conveyed to separate bins that are dedicated to the different grinding and flotation circuits. The upgraded crushing facility includes:
- one 30 ft. by 42 ft. jaw crusher with an installed power of 150 HP
- one 20 in. by 36 in. jaw crusher (standby unit) with an installed power of 75 HP
- one 5.5 ft. standard cone crusher with an installed power of 300 HP
- one 4.25 ft. standard cone crusher with an installed power of 200 HP
- one Nordberg HP500 crusher with an installed power of 300 HP
- one 5 ft. by 16 ft. scalping screen with apertures of 3/8 in.
- one 8 ft. by 20 ft. scalping screen with apertures of 3/8 in.
- other ancillary equipment, such as feeders, surge bins, conveyors, belt magnet, and metal detector.

With the upgrades, the crushing circuit is capable of crushing mill feeds at the rate of 2,500 t/d.

The plant consists of a conventional three-stage crushing circuit with the tertiary crusher in closed circuit with a screen. The crushed material is fed to each of the grinding lines, each consisting of a ball mill and related classification hydrocyclone(s) to grind the crushed mill feeds to a grind size of approximately 65% to 75% passing 200 mesh. The grinding mills used are 2.4 m diameter by 1.8 m long ball mills for Circuits #1 and #2, each with an installed power of 225 HP, and 3.2 m diameter by 4.6 m long ball mills for Circuits #3 and #4, each with an installed power of 1,000 HP.

A centrifugal gravity concentrator has also been installed in the grinding circuits to recover coarse precious metal particles into a high-grade gold/silver concentrate suitable for dispatching directly to a smelter.

The mill feed is processed in a conventional flotation mill that has four separate circuits and a capacity of 2,500 t/d. The four circuits include the following:
- Circuit #1 was used to process materials from the San Gonzalo Mine, which has been stopped since the end of 2019. The circuit was used to produce a lead concentrate containing gold and silver, as well as a zinc concentrate. The circuit has now been modified to process materials from the ET Mine and produces a copper flotation concentrate containing silver and gold. The processing rate is 250 t/d.
- Circuit #2 is used to process mill feed from the ET Mine and produces a copper flotation concentrate containing silver and gold. The processing rate is 250 t/d.
- Circuit #3 is used to process materials from the ET Mine and produces a copper flotation concentrate containing silver and gold. The processing rate is 1,000 t/d.
- Circuit #4 is currently used to process materials from the ET Mine, although it also p ........