The Pitarrilla Silver-Lead-Zinc Project is located in Northern Mexico. Image Representative. (Credit: Ingo Doerrie/Unsplash)
The cross section of an exploration drilling programme at the Pitarrilla Project site. (Credit: SSR Mining Inc./ PRNewswire)
As per 2022 Technical Report of the Pitarrila Project, the Indicated Mineral Resources (open pit and underground) at the property totals 158.6 million tonnes. (Credit: James St. John/ Flickr)

Pitarrilla is an undeveloped silver, lead, and zinc project located 160km north of Durango City in Northern Mexico.

The project is owned by Endeavour Silver Corporation, which operates two other high-grade, underground, silver-gold mines in Mexico.

In December 2022, the company filed a technical report on the project.

The Indicated Mineral Resources (open pit and underground) at the property totals 158.6 million tonnes.

This includes 491.6 million ounces silver (Ag) grading 96.4 grams per tonne (gpt), 1.1 million pounds (lbs) of lead (Pb) grading 0.31%, and 2.6 million pounds of zinc (Zn) grading 0.74% for a total of 693.9 million ounces of silver equivalent (AgEq) grading 136 gpt.

Endeavour Silver aims to assess different production alternatives for the project, including underground mining to strengthen its long-term production profile.

Several key permits for underground mining and development have already been secured.

Location and Site details

Pitarrilla property is located in Inde municipality on the eastern flank of the Sierra Madre Occidental mountain range in the central region of Durango.

The capital of Durango state, Victoria de Durango, is located 160km southwest of the property.

The property includes an area of about 4,950 hectares and consist of five contiguous mineral concessions. These concessions are entitled to SSD, a wholly owned subsidiary of Endeavour.

Pitarrilla has significant infrastructure in place which includes access to the national power grid. The project can be reached through a network of public roadways.

History of the project

The history of exploration on the property dates back to 1996.

In 2002, Silver Standard Resources acquired mineral properties in Mexico including the region covered by the Pitarrilla Project claim group.

Several diamond and reverse circulation drilling campaigns (RC) were undertaken by SSR between September 2003 and July of 2012.

SSR also issued a NI 43-101 technical report on the project and a pre-feasibility study was completed in 2009.

Endeavour Silver acquired the project from SSR Mining in 2022 for a consideration of $35m in cash, and another $35m in shares. SSR Mining will also be entitled to a 1.25% net smelter return royalty on the Pitarrilla property.

Geology, Mineralisation and Resources

The project’s deposits are hosted by deformed Cretaceous marine sediments and overlying Eocene (52 to 40ma) and Oligocene (32 to 28ma) volcanics, volcaniclastics, and intrusives.

The silver-lead-zinc mineralisation is identified in a metallogenic province called Central Mexican Silver Belt. It occurs as a vertically stacked system centred on rhyolitic dykes and sills.

The sulphide-associated mineralisation lies in the basement Cretaceous sedimentary strata and features aerially restricted and vertically extensive zone of disseminated and veinlet Ag-Pb-Zn (-Cu-As-Sb) sulphide mineralisation and strata bound massive replacement mineralisation within a polymictic conglomerate.

The inferred mineral resource estimate for the project (open pit and underground) is 35.4 million tonnes containing 99.4 million oz Ag grading of 87.2 gpt, 281 million lbs Pb grading 0.36%, 661 million lbs Zn grading 0.85% for a total of 151.2 million ounces AgEq grading 132.7 gpt.

Metallurgical testing and mining

In 2004, Silver Standard began testwork to gain a better understanding of the Pitarrilla deposit metallurgy and devise design criteria for the mineral extraction process.

This included initial scoping studies, flotation process development for sulphide ore, cyanide leaching development for oxide ore, and a combination of processes for the transitional ores (located between oxide and sulphide ore zones) and sulphide ores.

Overall, four floatation tests of the sulphide ore were completed.

The laboratory testing and pilot scale testing demonstrated that the sulphide mineralisation can be processed by flotation process treatment, while oxide mineralisation can be processed through cyanide leaching process.

Transitional mineralisation was amenable flotation process treatment, and flotation tailings can be processed by cyanide leaching process.

The latest MRE of the property is based on the premise that the deposit will be mined by open pit and underground mining methods.


The project has a well-established camp which includes general offices, welding workshops, mechanical workshops, general warehouse, clinic-medical services, and six core storage facilities.

The camp can accommodate 101 personnel, and includes dining facilities for 110 people.

Other facilities include accessible roads and several wells for water supply.

The project will receive power supplies from the national power grid via Subestacion Electrica Canatlán II substation located approximately 139km south of the plant site.

National power utility CFE will supply the power.

Key contractors involved

SGS Geological Services (SGS) prepared the 2022 technical report of the Pitarrilla Project for Endeavour Silver. The Mineral Resource Estimate in the report was estimated by an independent Qualified Person Armitage.

The first phase of the drilling programme was completed by Monarch Resources se Mexico in 1996. The drilling was carried out on the same property but the current Mineral Resource excludes the area.

In 2008, P&E Mining Consultants of Canada prepared a NI 43-101 technical report on the project.

In the Pitarrilla Project acquisition transaction with SSR Mining, PI Financial acted as Endeavour’s financial advisor and Koffman Kalef offered legal assistance.