Del Toro Silver Mine, Mexico

Key Data

Del Toro silver mine is located in the state of Zacatecas, Mexico. The underground mine is 100% owned by Canadian mining company First Majestic Silver Corporation (FMS) and covers an area of 393ha (943 acres).

"Underground techniques are being used to extract metals from Del Toro. Drilling and blasting are being carried out."

It was earlier known as the Chalchihuites Group of Properties and comprises polymetallic deposits.

Drilling at Del Toro was launched in 2005. The development of the mine will involve seven structures, namely San Juan, Perseverancia, Las Cotorras, San Nicolas, El Consuelo, El Carmen and El Zinc.

FMS is currently carrying out investigations on the San Juan and Perseverancia structures. A prefeasibility study (PFS) of the mine is underway.

Reserves at the Mexican silver mine

Measured and indicated resources of the Del Toro mine as of October 2008 stand at 1.3 million tons (mt) graded at 269g/t of Ag. The inferred resources are estimated at 1.8mt, graded at 306g/t Ag.

Geology of the surrounding area

Del Toro Silver mine lies between the Sierra Madre Occidental and Mesa Central volcanic terrains situated near the northwest border of Mexico. The terrains are characterised by tertiary Cretaceous rocks that comprise sedimentary calcareous and granodiorite intrusive sequences.

The San Juan is conceived to be the oldest structure in the Chalchihuites mining district. It spans a strike length of 100m to 300m and depth of 200m. It is enclosed by igneous rocks of limestone, quartz and monzonite.

The La Perseverancia structure comprises two chimney-like ore bodies. The chimneys are 15m to 30m long and 6m to 10m wide. Mineralisation occurs in breccia with break ups of igneous rock and skarn.

Mineralisation of the Del Toro silver mine

Mineralisation at Del Toro occurs in veins, breccia pipes and mantos. Minerals hosted in the San Juan structure are hosted in Indidura formation. The minerals occur in vein type ore bodies in the form of skarn and quartz-monzonite compositions.

The mineralisation includes silver, lead and zinc concentrates in the upper parts of the veins and chimney type ore bodies.

The ore extracted from the San Juan hosts oxidised mineralisation with cerussite, limonite, galena, sphalerite, argentite and a gangue of quartz and calcite.

The perseverancia structure contains oxides and carbonates including cerussite, cerargyrite, smithsonite and haematite. Sulphide ore is found at the deepest level of the structure along with galena, sphalerite, argentite and a gangue of quartz and calcite.

Production rates at the Mexican silver mine

Production at the Del Toro mine will begin in 2012. The mine is expected to produce 3.25 million ounces (moz) of silver equivalent in 2012. It will become the fourth producing silver mine of FMS.

Mining methods used

Underground techniques are being used to extract the metals from Del Toro. Drilling and blasting are being carried out by using drills, aluminium nitrate and fuel oil (ANFO) explosives respectively.

Trackless diesel-powered mining equipment, including load haul front-end loaders, dump trucks and electro-hydraulic drill jumbos, will be used to perform the mining operations.

Mine development, exploration and production are being contracted to mining firms. MECOMIN is the prime contractor involved in the development of the mine. Underground haulage work is being carried out by Armando Alvarado.

Ore processing techniques

The ore extracted from San Juan will be transferred to the La Parrilla Processing plant by means of dump trucks for further processing.

"Del Toro silver mine is located in the state of Zacatecas, Mexico."

The La Perseverancia ore will be conveyed either to the La Parrilla processing plant or to the smelter in Torreon.

The recovered ore will contain oxides, sulphides and lesser quantities of lead, zinc, gold and copper. The oxide ore will be processed by using a cyanide leaching circuit which produces silver doré.

The floatation circuit will yield silver-rich lead and zinc concentrates from the sulphide ore.

First Majestic received permission from the Mexican authorities in January 2010 to build a 1,000 tons a day (tpd) floatation circuit at the Del Toro mine site.

Construction of the circuit began in April 2011 and foundations were laid in September 2011. The throughput of the floatation circuit is planned to be increased to 2,000tpd in 2013.

Aerial view of the Del Toro silver mine.

Underground techniques are being used to extract quality metals from Del Toro.

Silver ore extracted from the Del Toro silver mine.

The Del Toro mine lies between Sierra Madre Occidental and Mesa Central volcanic terrains.