At the Bolivar Property, the volcanic rocks strike northwest and dip gently to moderately to the northeast.

Skarn alteration and mineralization at the Bolivar Property is hosted primarily in a package of sedimentary rocks that occur as a layer or lens within the LVS (Reynolds, 2008). All sedimentary units have undergone low grade metamorphism. The lowermost sedimentary horizon observed is a dolostone which ranges from 24 m to 40 m in thickness. The lower part of the dolostone horizon is interlayered with siltstone. To the south, progressively less of the sedimentary sequence is cut out by granodioritic intrusive rocks and the dolostone is observed to be underlain by a siltstone horizon.

The Bolivar deposit is classified as a high-grade Cu-Zn skarn and exhibits many characteristics common to this type of deposit. The term ‘skarn’ refers to coarse-grained calcium or magnesian silicate alteration formed at relatively high temperatures by the replacement of the original rock, which is often carbonate-rich.

The dikes locally cut the granodiorite, have planar, chilled contacts, and are generally finely crystalline. Both their texture and crosscutting relations suggest that the dikes are younger and shallower than the granodiorite. Both granodiorite and andesite dikes have alteration and locally skarn along their contacts. In addition, endoskarns, which are skarns of igneous origin that form within the granite mass itself, affect both the granodiorit ........

Sub-level stoping and room and pillar mining methods are currently used in the main areas of the mine to obtain a production rate of 5,000 tpd.

Using the resources estimated by SRK Consulting through December 2019, Sierra Metals performed a growth analysis to determine how the Bolívar Mine could achieve sustainable production of 7,000 tpd - 15,000 tpd. The analysis indicates that the production objectives are achievable through the expansion of the sub-level stoping mining method in the new production areas, which will allow the sustainability of the operation. A new configuration of the mining method will allow greater recovery of resources and production rates.

A new configuration of the mining method will allow greater recovery of resources and production rates.

Current production at Bolivar comes from the El Gallo Inferior, Chimenea 1 and 2 and the Bolivar West mineralized zones. Mineralized material is currently hauled to the surface using one of several adits or declines accessing the mineralized zones and is then dumped onto small pads outside the portals. The mineralized material is then loaded into rigid-frame, over-the-road trucks and hauled on a gravel road approximately 5.1 km south to the Piedras Verdes Mill.

Future production will include mineralized material from Bolivar Northwest (BNW). The Bolivar NW mineralized zone is further broken down into BNW 1, BNW 2, BNW 4, BNW 6, BNW 7, BNW8 and BNW 9.

The longho ........

The Piedras Verdes processing plant can be adapted to process 10,000 tpd and would require:
• Temporary shutdown to overhaul equipment;
• Purchase of mobile jaw and cone crushers; and
• Overhaul and reintroduction of idle equipment.

The crushing stage is supplied with mineralized material hauled from the mine site using contractor operated haul trucks. A typical haul truck has approximately 20 tonnes capacity and delivers mineralized material from the mine area to the primary crusher’s mineralized material stockpiling area. Trucks can dump directly to the primary crusher or alternatively, to one of several stockpiles. Typically, a front-end loader reclaims mineralized material from the stockpiles and then feeds the jaw crusher.

The crushing plant is fed through a hopper equipped with a 20-inch x 20-inch static grizzly that discharges to a jaw crusher operating in open circuit. The nominal four-inch material discharging from the jaw crusher is classified by two double-deck vibrating screens. The top screen is two inches by one inch and the bottom screen is 3/4 inch by 3/8 inch. Material smaller than 3/8 inch becomes the final crushed product that is transferred to two silos having an individual capacity of 1,000 tonnes each. The vibrating screen’s oversize feeds a secondary crushing stage consisting of two cone crushers. The top screen is conveyed to a Sandvik HC660 cone crusher and the bottom screen oversize is conveyed to a Metso HP-300 cone crusher. The cone crusher’s discharge joins the primary crusher’s discharge and feeds the double-deck vibrating screens.

Feed to the grinding circuit is sourced from two 1,000 tonne silos that hold the final crushed product from the crushing plant. The grinding circuit consists of conventional ball mills operating in closedcircuit operation with hydrocyclones. Two 9.5 ft x 14 ft ball mills operate in parallel, each one in closed circuit with a hydrocyclone cluster. The two ball mills underwent complete overhauls during the end of 2017 to improve mechanical availability. The hydrocyclones were changed from D26 to D20 to improve plant stability. The product size in the cyclone overflow ranges between 34% and 48% passing 75 micrometers, with an average size of 43.5% passing 75 micrometers. The hydrocyclone overflow feeds the flotation circuit. The hydrocyclone underflow stream is returned to the ball mills for further size reduction.

- subscription is required.

- subscription is required.