The San Martín gold-silver district hosts classic, medium-grade gold-silver, epithermal vein deposits characterized by low sulphidation mineralization and adularia-sericite alteration. The San Martin veins are typical of most other epithermal silver-gold vein deposits in Mexico in that they are primarily hosted in the Upper Cretaceous black limestone and calcareous shales of the Soyatal-Mexcala Formation. Tertiary Lower Volcanic series of rhyolite flows, pyroclastics and epiclastics, overlain the sediments.

Mineralisation is generally made up of breccia that commonly is concordant with a limestone/shale contact (in the San Martin and San José areas) which forms the relatively steeply dipping “Tronco” and “Mantos” oreshoots, these veins contact the younger volcanic flows (dacite and ignimbrite) where they have formed the more horizontal portions of the deposit. The mineralized economic breccia grades from 30 g Ag/t to 250 g Ag/t. Exploration has been concentrated along the NE trending breccia zone however evidence of a northerly trend in area 30 and 31 leads to suspect possible other structures together with 2.0 g Au/t to 30 g Au/t over widths that vary from 1.5 to 17.0 m but averaging 4.0 m.

Mineralization at San Martín occurs in association with an epithermal low sulphidation, quartz-carbonate, fracture- filling vein hosted by a structure trending approximately N40°- 60°E, dipping to the 50° to 90° to the southeast.

The San Martin structure has been known in different stages of exploration and has adopted several names, San José, San José II, San Martín, Cuerpo 28, Cuerpo 29, Cuerpo 30 and Cuerpo 31. The structure itself is offset by a series of faults of northeast trending that divides the oreshoots. The structure behaves vertical at the San José and San Martin areas (Tronco) and becomes flatter from Cuerpo 28 to 31 (Mantos), and mineralization follows the planes of the folded rocks.

The San Martin vein itself has been known underground traced for 2 km along trend, with widths between 1.5 to 10 metres and averages approximately 4.0 m. A secondary mineralized vein is located, both in the footwall and hangingwall, of the San Martin vein, on the wetern limb of the local fold that contains the mineralization. This structure is the Santa Elena and represents a good target for exploration to the NE and SE of San Martin.

The San Martin deposit is composed by a tabular, vein-like subvertical mineralised structure that becomes to a sub-horizontal mineralised structure or “manto-like” close to surface. This mineralised structure is recognized for over 2 km along strike, with thicknesses between 1.5 and 17 metres and 400 m of vertical extent or “favourable zone”. In general, the mineralisation is hosted in the contact of limestone-shale of Soyatal-Mexcala Formation and associated to a silicified rhyolitic dike.

Mine production operations are in two distinct underground zones and one under one small open pit operation. Current mining is from zones, which are contiguous to, or nearby, earlier mined out areas.

The two underground zones are known as San José II and San Martín, while the open pit is the near surface remnants is now a closed operation. Production operations have been underway at the San Martin mine since May 1994. On top of the big breccia-vein the structure becomes a manto-like. Here the Cuerpo 28 and Cuerpo 29 orebodies have been exploited partially since 1998. A set of faults crosscut the structure and thrown down the continuous oreshoot and split it into several segments where Cuerpo 30 and Cuerpo 31 have been found. In 2001 the exploration of high-grade gold bodies called "Mantos" began. The first of these oreshoots was the Body 28.

The orebody geometry and geotechnical attributes of the ore and host rocks, in both underground zones, resulted in the selection of mechanized, trackless, room and pillar stoping, with post waste rock backfill and a poor mix of waste and cement, as the most suitable mining method for ore extraction. Ore recovered from these operations is hauled to surface by truck to the mill infrastructure, where it is crushed and milled.

The San Martin underground mine is accessed through a tunnel located at the 2,050-meter level.

Since 2007, SIM (Starcore International Mines) has been in control of the day- to-day mining operations at the San Martin Mine Project. SIM assumed control of the mining operations from a local mining contractor in order to allow for more flexibility in operations and to continue optimizing the costs. The San Jose mine operates on two 10- hour shifts (contractors) 20 by 8. The San Martin works 3 shifts 8 hours each, six days a week. The supervisors are in shifts of 20 by 8 for body 28 and 10 by 4 for San Martin.

The facilities of the plant are designed to process gold and silver ore at a rate of 850 tpd, with the capacity of 1,100 tpd, in a series circuit that includes crushing, milling, leaching, a system of countercurrent washing by decantation and Merrill Crowe for the recovery of the values. The flow diagram of the plant consists of the following processes:

- Crushing and transport
- Storage and claim
- Primary and secondary milling
- Dynamic leaching with gaseous oxygen injection
- Counter-current washing circuit by decanting
- Precipitation of values (Merrill Crowe)
- Precipitate drying
- Refinery
- Filtering of tailings
- Storage of dry tailings
- Reagent preparation systems and their distribution.

In the crushing area, the ore is reduced to ¼ in., to be fed to the primary ball mills and later to the secondary vertical mill to obtain a 70% product at 74 microns. This is fed to the dynamic leaching circuit wher ........