The silver-gold mineralization at Alamo Dorado is predominantly fracture-controlled and associated with moderate to intense pervasive silification. About 50 percent of the silver mineralization is related to strongly fractured rhyodacites and about 30 and 10 percent in the rhyolites and dacites, respectively. The main silver mineral at Alamo Dorado appears to be chlorargyrite which is a silver mineral derived from a silver chloride complex occurring along with the quartzpyrite minerals filling the fractures. The gold mineralization occurs as free, micron-size particles and/or in the crystal lattices of micro-crystalline pyrite.

Alamo Dorado is a conventional surface mine that utilizes hydraulic shovels, front end loaders, and mechanical trucks on 5 metre high benches. Ore control is carried out by sampling blast holes to provide closer spaced sample data for marking the ore and waste boundaries during mining.

Ore is treated by conventional crushing and semi-autogenous and ball mill grinding followed by thickening, agitated cyanide leaching, leach residue filtration, direct electrowinning to produce a cathode sludge, AVR (acidify, volatilize, and re-neutralize) cyanide recovery and recirculation, leach residue washing with AVR product solutions, dry stack tailings, and conventional silver and gold doré production from melting of the cathode sludge. The nominal design treatment rate is 4,000 tonnes per day of ore on a 24 hour per day schedule, but Alamo Dorado regularly exceeds this processing rate. The mine’s tailings treatment process recovers approximately 45% of the sodium cyanide used and also neutralizes mill tailings, thus reducing the mine’s environmental impact and reclamation costs.