Mithril is currently executing a fully funded drill program at the Cometa Project in the Copalquin District following its successful maiden drill program completed during the second half of 2020.

The Copalquin District mining concessions cover 70km2 and include dozens of historic mines and workings. The concession area is located approximately 4 hour drive from the city of Culiacan and 8 hour drive from the city of Chihuahua via highway 24. The town of El Durazno is located approximately 20km east of the concession area. The Copalquin airstrip is serviced several times daily from Tamazula (15 minutes) and Culiacan (30 minutes).

Currently Mithril has one man-portable diamond core (HQ size) rig drilling at Copalquin as it builds up its geologic knowledge of the district and in particular, the Cometa project targets. In H2 2020, we completed over 7,000 metres of diamond core drilling and discovered the of the top of a large hydrothermal system within the Cometa Project area which includes the historic La Soledad and El Refugio multilevel mines that operated in the second half of the 19th century.

Drilling is continuing to develop the El Refugio and La Soledad target as significant contributors to the Copalquin District resource potential.

Figure 1. Copalquin district map for full mining concession area

Figure 2. Geologic model section

Figure 3. Vein Model & Intercepts at the Cometa Project

Gold equivalent grades calculated at 70 g/t Ag = 1 g/t Au, using gold price of USD1,610 per ounce and silver price of USD23 per ounce.

  • Oblique view of vein models for El Refugio & La Soledad
  • Deeper holes to intercept probable Refugio-Soledad vein intersection
  • Deeper holes at El Cometa since it is now understood to be same vein structure as Refugio

Figure 4. Grade Thickness Increased with Depth at the El Refugio target – Cometa Project

Gold equivalent grades calculated at 70 g/t Ag = 1 g/t Au, using gold price of USD1,610 per ounce and silver price of USD23 per ounce.

  • Longitudinal section at El Refugio showing drill hole pierce points
  • Grade domains show grade has increased with depth


The Copalquin Project lies within the Sierra Madre Occidental physiographic province of north-western Mexico. The project is underlain by andesitic volcanics of the Cretaceous-Tertiary Lower Volcanic Series. A Tertiary granodiorite to monzonite pluton intrudes the andesite and much of the area is capped by Tertiary rhyolite ignimbrites of the Upper Volcanic Series. Mineralisation is thought to be contemporaneous with the eruption of the Upper Volcanic Series.

Semi-continuous low-angle breccia zones have formed within the andesite parallel to the granodiorite contact. These zones include the El Cometa breccia and the Los Reyes breccia. The geometry of these zones is similar to the nearby El Gallo silver deposit of McEwen Mining which is also formed in a series of breccias parallel to the contact between intrusive rocks and Lower Volcanic Series andesite.

A series of high angle normal faults strikes northwest and dips to the northeast including the Refugio, La Soledad and La Constancia structures which host veins mineralised with gold and silver. North-south striking, west dipping faults at San Manuel also host mineralized veins.

Both the low-angle breccias and the high-angle faults host extensive zones of mineralised quartz breccia. It is likely that the low angle zones developed as tectonic breccias during the intrusion of the granodiorite and were later mineralized by hydrothermal activity related to the eruption of the Upper Volcanic Series.

Large areas of argillic alteration occur across the concessions. The alteration forms haloes adjacent to the known structures and large zones where structures have not been identified. Argillic alteration is indicative of widespread penetration of hydrothermal fluids into the surrounding rocks and suggests a long-lived hydrothermal system was active at Copalquin.

The alteration from Refugio to Los Reyes is over 2,000 meters long and from 100 to 400 meters wide. It is expected that the widest zones are related to shallow-dipping portions of the Cometa-Los Reyes structures where the structure is nearer the outcrop surface. Similar alteration is present well to the west at El Platanal and well to the east at Constancia. It cannot be stressed enough that this strong, widespread argillic alteration forming a large-volume halo well out from the veins is the observable geologic characteristic that identifies Copalquin as a major epithermal centre.

Figure 5. Central 1,600 Ha of the 7,000 Ha mining concession area showing 2020 to March 2021 drilling highlights and best rock channel samples from other historic mine workings.

Copalquin Mining District History

  • Discovered in the 1848, production ceased during the Mexican Revolution.
  • El Refugio first mined in 1849. By 1897 there were 10 head stamp batteries installed with cyanidation plants.
  • 1935 the company Minera CIBOLA milled ore from the San Manuel and El Cometa mines.
  • Detailed sampling of some workings by Industrial Mineral Mexico S.A. de C.V. (IMMSA) in 1983.
  • 1995 Alta Pimeria and Kennecott outline a potential target of a million ounces of gold and 50 million ounces of silver.
  • 1997, Bell Coast Capital Corp (BCCC) conducted a helicopter supported, 31-hole, 2,500 m diamond drill program from 6 to 8 drill pads. This first-pass drilling program returned excellent results, but BCCC withdrew from the project due to difficulty in acquiring financing during a period of very low gold and silver prices.
  • BCCC completed an extensive program of geochemical sampling and mapping, resulting in the discovery of three large anomalies.
  • UC Resources explored at Copalquin from 2003 – 2007, drilling 39 diamond core holes for 4,200m. UC also completed geochemical sampling and an ASTER study. UC experienced funding difficulties and ceased activities late 2007.

Historic Articles

Articles in the Engineering and Mining Journal 1897 and 1900 give some details about past developments and production of gold and silver from the Copalquin Mining District. Click the links below to open the articles in a separate window. Close the window to return to the site.

Engineering and Mining Journal 12th May 1900
Engineering and Mining Journal 21st August 1897
Engineering and Mining Journal 4th September 1897

Historic Drilling Reports

Past Releases from UC Resources on the Copalquin District