The mineralization is typical of epithermal vein structures with banded and drusy textures. Within the San Dimas District, the veins occupy east-west trending fractures, except in the southern part of Tayoltita where they strike mainly northeast, and in the Santa Rita mine where they strike north-northwest. The veins were formed in two different systems. The east-west striking veins were the first system developed, followed by a second system of north-northeast striking veins. Veins pinch and swell and commonly exhibit bifurcation, horse-tailing and sigmoidal structures. The veins vary from a fraction of a centimetre in width to 8 m, but average around 1.5 - 2.0 m. They have been followed underground from a few metres in strike-length to more than 1,500 m. An example of a vein with mineralization in the Favourable Zone extending for more than 2,000 m in the Tayoltita Mine, the San Luis Vein.

The San Dimas Mine operation includes four underground gold and silver mining areas: the West Block (San Antonio mine); the Sinaloa Graben Block; the Central Block and the Arana Block (the Santa Rita mine). Vein thickness varies from 0.1 metres to 8 metres with the average approximately 1.9 metres. Some veins have a strike length of more than 1,500 metres. Vein dips vary from about 35 o to sub-vertical, the latter being decidedly more prevalent. The general mining recovery factor is about 95%, while that for sill mining is about 75%.

Typical mining of the vein systems is by mechanized cut-and-fill and long-hole, using drill jumbos or jacklegs, pneumatic long-hole drills and load-haul-dump machines, with primary access provided by adits and internal ramps from an extensive tunnel system under the steep, mountainous terrain.

The basis for ore haulage at San Dimas is load-haul-dump (“LHD”) equipment feeding trucks for haulage to the portal and then plant stockpiles. In the Tayoltita mine, the LHD equipment load rail wagons for haulage to the Tayoltita mill crushing plant. Development waste is generally moved to stopes as fill.

The San Dimas mining complex includes one milling facility at Tayoltita with a 2,500 tpd capacity to process the production from the active mining areas. The Tayoltita mill has a conventional Merrill-Crowe process flowsheet that employs crushing and grinding followed by cyanidation and zinc precipitation for recovery of gold and silver.

Leaching is completed in a series of tanks providing minimum of 75 hours of leach residence time. The pregnant solution is recovered in a counter current decant (CCD) circuit with the gold and silver recovered from solution in a zinc precipitation circuit. [2014, San Dimas Tech.Report, p. 103]

Refining uses an induction furnace to produce 1,000 oz silver and gold doré bars (average 98% pure). [2014, San Dimas Tech.Report, p. 103]

At San Dimas, the Company plans to install a new 3,000 tpd HIG mill circuit in 2020 to further improve recoveries and reduce operating costs. The delivery of the HIG mill is expected in the f ........