Commodities: Copper-Silver-Gold

Location: Chihuahua, Mexico

Ownership: 100%

Land Package: 15,217 hectares

Deposit type: Copper-Silver-Gold

Operation: Underground mine, room & pillar; flotation plant



For the 3 Months Ended June 30, 2019 and 6 Months Ended June 30, 2019, the Bolivar Mine produced the following:

Bolivar 3 Months Ended 6 Months Ended
June 30, 2019 June 30, 2018 June 30, 2019 June 30, 2018
Tonnes processed (mt) 326,208 272,040 589,445 531,415
Copper (000 lb) 5,187 4,737 9,056 9,099
Zinc (000 lb) 0 0 0 0
Silver (000 oz) 152 110 282 230
Gold (oz) 1,586 911 2,685 1,959

A detailed summary of production is presented in the Company's July 15, 2019 press release.


On July 5, 2018, the Company released an updated NI 43-101 compliant reserve and resources estimate for its Bolivar Mine, completed by SRK Consulting, Inc. of Denver, Colorado.

Category Tonnes
(M lb)

Proven - - - - - -
Probable 7,925 19 0.86 0.25 1.14 199
Proven & Probable 7,925 19 0.86 0.25 1.14 199


Measured - - - - - -
Indicated 13,267 23 1.04 0.30 1.37 402
Measured & Indicated 13,267 23 1.04 0.30 1.37 402
Inferred 8,012 22 0.96 0.42 1.35 238


  1. The effective date of the mineral reserve and resource estimate is October 31, 2017.
  2. Details of the estimate are provided in the Company's May 22, 2018 press releases with a NI 43-101 technical report to be filed on SEDAR on July 5, 2018.
  3. Measured, Indicated and Inferred Resources include Proven and Probable Reserves. CuEq is based on the following metal prices: US$18.25/oz Ag, US$3.00/lb Cu and US$1,291 Au. Totals for proven and probable are diluted for internal waste.
  4. Mineral resources that are not mineral reserves do not have demonstrated economic viability.

(Complete details of the updated reserve and resource estimate will available in the upcoming NI 43-101 technical report - please click here)


Sierra Metals owns 100% of the Bolivar mine located in state of Chihuahua, Mexico, Bolívar is a copper-silver-gold underground mine using room-and-pillar mining method. The property comprises 12 mining concessions covering approximately 6,616 hectares within the municipality of Urique, in the Piedras Verdes mining district of Chihuahua, Mexico. Sierra Metals purchased the claims for the Bolívar Mine between 2003 and 2004, and has conducted mining activities at the Bolívar Mine since February 2005. Bolívar is a district-scale property considered prospective for new discoveries of precious metal and bulk-tonnage copper-skarn deposits.

During 2011, the Company completed the construction of the Piedras Verdes Mill, located 6 km from the Bolivar Mine. The mill had an initial capacity of 1,000 tpd, resulting in a declaration of commercial production at Bolivar in November 2011. The mill was expanded to 2,000 tpd in 2013 and currently produces a copper-silver-gold concentrate at 3,000 tpd. At the current production rate, Bolivar's current reserves provide for more than 7 years of mine life.


The Bolívar Mine property is located in the municipality of Urique, approximately 255 km southwest of Chihuahua, Chihuahua, and roughly 1,250 km northwest of Mexico City. The project area is situated in the rugged mountainous terrain of the Sierra Madre Occidental, bounded by Copper Canyon, 50 km north and east of the mine, El Fuerte River, 18 km south of the mine, and the villages of Piedras Verdes, 1.5 km north, and Cieneguita, Chihuahua, 7.5 km north and west of the mine. The geographic center of the property is located at approximately 27° 05' N Latitude and 107° 59' W Longitude.


Road access to the Bolívar Mine is from Chihuahua City, 325 km along paved roads and a further 70 km by all-season gravel roads to Piedras Verdes village, then 2 km south to the minesite.


In March 2015, the Agua Caliente power substation was connected to the new 115kw line, providing power to the Piedras Verdes processing plant through the 33kw line from the substation. Prior to this connection, production had used a less reliable grid connection supplemented with diesel generators and was prone to shutdowns and disruptions. The current interconnection should eliminate these problems.

The villages of Piedras Verdes and Cieneguita are located close to the Bolívar mineral concessions, with a combined population of approximately 1,000 people (approximately 750 for Cieneguita and 250 for Piedras Verdes), including some of the mine employees. Company vehicles provide transportation to the Bolívar Mine.

Industrial water is obtained from the Piedras Verdes Dam, a reservoir that is owned and operated by Sierra Metals. The reservoir drains to El Fuerte River, located approximately 2 km south of the Bolívar Mine. According to Sierra Metals, water from the Piedras Verdes Dam is sufficient to supply mine operations, exploration, and mill requirements. Potable water is available from local sources and is sufficient for mining operations.


Small-scale mining was conducted in the Piedras Verdes district during the Spanish Colonial days, but historical records of production were not maintained and production values are unknown.

An estimated 300,000 tonnes of mineralized material was reportedly mined from 1998 to 2000, while the Bolívar Mine was under the control of Bencomo Family, but production records for this period are not available.


The Bolivar Property is situated within the Piedras Verdes Mining District, which is within the major north-northwest trending Sierra Madre Precious Metals Belt extending across the states of Chihuahua, Durango and Sonora in northwestern Mexico. Late Cretaceous – Early Cenozoic sedimentary and volcanic rocks underlie the district (Lower Volcanic Series or "LVS").

In the Bolivar area the LVS is reported to be approximately 750 m thick. The rocks of the LVS are overlain by younger continental rhyolitic and dacitic ignimbrites (up to 1.5 km thick) of the Upper Volcanic Suite ("UVS"), which are interpreted to be Middle Tertiary in age. In general, rocks in the area trend northwest and dip gently to the northeast. These rocks are also cut by several northwest and northeast-trending faults.

Skarn-type Cu-Zn-Ag-Au mineralization in the Bolivar area is structurally controlled and forms mineralized zones that are close to structures. Mineralized zones occupy pre-existing fault structures and extensional openings formed during mineralization. The mineralized zones are dominated by calc-silicate minerals and variable quantities of quartz, calcite, and chlorite. Sphalerite and chalcopyrite are the predominant sulphides, commonly ranging from 5% to 30% (combined), with occasional massive sulphide zones. Sulphides occur within the carbonate rocks, which they replace, a common feature in skarn-type mineralization.


The El Gallo ore body consists of two sub-deposits, "El Gallo Superior" (Upper) and "El Gallo Inferior" (Lower). Currently the Superior deposit is being mined by the room and pillar method using ramps. Current mining has shown that the hanging wall and foot wall consist of competent and strong formations. Mining of the Inferior deposit will require a modified room and pillar method of mining to accommodate the physical characteristics of the deposit. The dip of the Inferior deposit requires that access to the room and pillar stoping areas be achieved by excavations at a maximum ramp inclination of 13%, which will allow rubber-tired equipment to operate.


The Piedras Verdes Mill was built in 2011 with an original capacity of 1,000 tpd and was increased to 2,000 tpd in 2013. The mill uses the flotation process to produce a copper-silver-gold concentrate. Further expansion of the mill to 2,500 tpd is planned in H2 2015.


In 2014, underground drilling expanded the copper-gold-silver mineralization at the Bolivar NW deposit while surface sampling and drilling continued to highlight the promising La Sidra silver-gold quartz vein system, which has been traced on surface over a 2.5 km strike length.

The 2015 exploration program for Bolivar includes over 21,000 meters of drilling with 8,700 meters allocated toward resource expansion and 12,500 meters for exploration. Exploration efforts will continue to focus on upgrading resources to reserves and expanding known mineralization in the vicinity of the El Gallo area, including the Bolivar NW, Alta Ley and Step Out zones. Exploration drilling will focus on several high-value targets such as La Sidra, Lilly Norte and the Nathalie Fault area.


At Bolivar, Sierra Metals completed the expansion of the Piedras Verdes plant from 2,000 tpd capacity to 2,500 tpd in H2 2015.

The 2016 exploration program is directed toward expanding and upgrading the mineral reserves and resources at Bolivar as well as following up on a number of high-priority exploration targets.