The Aguila Project area is dominated by multiple volcanic domes of various scales that compose the district geology. These volcanogenic features are superimposed on a pre-volcanic basement of sedimentary rocks. Gold and silver mineralization in this district is related to the manifestations of this classic volcanogenic system and is considered epithermal in character. The Aguila Project mineralization occurs as structurally-controlled epithermal deposits in veins and stockwork zones consisting of concentrations of sulfides containing gold, silver, lead, copper, and zinc, associated with gangue minerals such as quartz, calcite, and other minor elements. Primary sulfide mineralization consists of pyrite, galena, sphalerite, chalcopyrite associated with minor amounts of argentite and silver sulfosalts.

GRC’s exploration investigations have been mainly focused on the Aguila open pit and Arista underground mine areas. These areas include the significant Aguila, Arista, Baja and Aire veins as well as other ancillary mineralized structures. A potential new area of mineralization, referred to as “Switchback”, has been identified approximately 500 meters northeast of the Arista deposit, for which drill results showed multiple veins over a 40 to 100 meter wide alteration zone containing numerous mineralized veins associated with rhyolite dikes and hosted in andesite, similar to the Arista vein system. Other mineralized zones and properties have been investigated, including some preliminary drilling in areas such as Escondida, Chacal and Salina Blanca on the Aguila Project, and the Margaritas, Alta Gracia and Rey properties.

The Arista Mine was expanded in 2016 with the development of the Switchback vein system. [2019 Annial Report, P.6]

There are two main mining methods used in the Arista underground mine: 1) overhand mechanized cut and fill (CAF) and 2) long-hole open stoping (LHOS) with delayed fill.

Gold Resource Corporation currently processes all of the Arista underground mine ore through the flotation circuit at the Company's El Aguila mill. The plant was built near the mine site and consists of two separate production circuits: a differential flotation circuit (sulphide ores) and an agitated leach circuit (oxide ores). The current nominal capacity of the flotation circuit is 1,500 tonnes per day, while the agitated leach circuit has a nominal capacity of 300 tonnes per day.

The flotation circuit produces three types of high-grade concentrates: a copper concentrate with gold-silver; a lead concentrate with gold-silver; and a zinc concentrate with gold-silver. All concentrates are marketed to a broker in México.

In 2014 we completed a doré processing facility. The Aguila processing facility is flexible in its ability to process several types of mineralization. It has a differential flotation section capable of processing polymetallic ore and producing up to ........