Foreign Trade: ALLUVIAL GOLD PROJECT - Adrián Mercado
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San Juan Province


The mineral ore is located at the North West side of San Juan City, Jachal Department, Huachi Mining District. ​

Access via: Coming out of San Juan City, to the Norh by National Route Nº 40 in 158 km we arrive to San José de Jachal City, which is the head of the department. The Mineral Ore can be reached through a road that is projected which will have a total extention of 45 km from San José de Jachal City to Las Tolas Post (coordinates S: 29º56¨45” - W: 68º53¨30”). This is the place of the base camping where the primary exploitation will bed (trituration and primary concentration of the mineral). This road will be a benefit that will save several km of travel, because the actual road has more than 120 km and makes a rodeo for several mining streaks. ​

The goal of this project is to exploit the alluvions and eluvials in Quebrada del Agua Amarga. For this, access roads, campings, and feasibility studies will have to be made in order to widen the exploitation of the aforementioned gorge. ​

This exploitation is laid out on existent studies called out before, exploration mining carried out by Geologist Dr, Manuel Rodriguez Murillo (official reports are in the San Juan Province Mining Ministry and were made in years 1980-1981) and according to the values obtained in the entire alluvion in Quebrada del Agua Amarga, estimations are between 8 grams and 15 grams of gold each ton. ​

In order to carry out this exploitation without applying contaminant chemicals, gravimetric concentration of the mineral is only carried out.


The entire project is all located in Quebrada del Agua Amarga, known for the many vein-shaped structures in there hold which gave place to many very important mining in XIX and XX centuries. ​ Geologically, it comes out of the mining deposit a volcanic cover with andesitic composition and a wide variety of pyroclastic rocks (agglomerate, breccias, etc.), affected by hydrothermal alliterations. At East of Quebrada del Agua Amarga surge intrusive objects with a dacitic composition, while at South predominate other intrusives, showing in both cases processes of Hydrothermal Alteration. ​

This fragment facilitates the circulation of hydrothermal solutions and the filling of those solutions with sulfur (chalcopyrite, gold-bearing pyrite, galena, silver, etc,) with quartz or calcite as gangue mineral. ​ In the district, more than 100 vein-shaped structures have been recognized, with are 3 Km large and have a power that goes up to 2 m. Taking as a reference Quebrada del agua amarga, two big sectors can be shown: ​

a)- Occidental Sector: Between the veins with many variables are the ones from Guanaco, Sta. Filomena, La Jachallera, etc (Murillo, 1980). ​

b)- Oriental Sector: It concentrates the biggest quantity of veins where it can be found: Bronce, Sentazon, Los Andes, Oro Rico, etc. (Murillo, 1981). Huachi mineralization is not restricted only to vein-shaped structures, because in the central portion there are alluviums and eluvials from Quebrada del Agua Amarga in which slopes the system has highly altered porphyries and they are partially covered by dacitic rocks, which permits to storage an interesting amount of substances with a good grade of use (gold, silver, copper, zinc, mercury, etc.). The field (which has inside the alluvial and eluvial mineral ores) has 1300 Ha 4.256,06 m2 of uncultivated land. In its central part it counts with a gorge (Quebrada del Agua Amarga) which has an important dragging of alluviums and eluvials of Au, Ag, Pb, Cu.


Gold is found in nature with very few exceptions as a native metal. It is presented in veins of gold-bearing rocks, associated with other metals and in the form of dust or rounded or flatted grains, known as nuggets, in sand deposits and riverbeds. ​ The high density of gold (15,3 kgL-1 to 19,3 kgL-1 according the amount of other associated metals), makes possible to apply treatments based on gravitational concentration. ​ The hydrophobic character of native gold allows its recuperation by flotation. ​ Gold will extracted by gravimetric concentration. ​

The exploitation plant will be formed for: ​

A - Access, Campings and Infrastructure ​

In order to develop the project, the access road to the mining ore must be realized first. It has a longitude of 45 km from Jachal City to Las Tolas Post. ​

The access to the place is by the gorge “Los pajaritos” (Little Birds), and having into account that there is an existing track of mining trace that will allow us to have a longer-lasting access. The last 20 km to the property should be repaired, conditioned and extended and it will be needed also to make 10 km of road making a demolition in order to make a development in a 300 m cliff, up to reach to Oro Rico Post and the different alluviums.

B - Trituration and Primary Concentration

Plant Las Tolas Post (gross concentration) ​ B1 - Gross Gold Recuperation in a centrifugal force concentrator: ​ In Las Tolas Post classification, trituration and grinding could be made in order to carry out with gravitational concentration equipment a first pre-concentration in that place. ​

This pre–concentration can be performed with an equipment type Knelson, Falcon, Jigg, spiral concentration, etc. The main idea is to transport the enriched mineral to finish its concentration and to melt it in the industrial park zone in Jachal City. The Knelson centrifuge concentrator, used in the concentration of gold minerals, has proved to be good equipment because it makes the separation with a high efficiency. It has a high process capacity and its operative and maintenance costs are relatively low. ​ It is mainly formed by a polyurethane truncated cone that rotates at 400 rpm, and its internal surface is formed by a series of horizontal partial rifles of equal depth. The speed of rotation movement generates a centrifuge strength of 60g, which carries out the material particles to periphery, where mineralogic particles with the biggest weight tend to enter in the inter-rifle spaces, as the light particles are transported to the external upper part. ​

C - Civil Engineering Work ​

There are all the necessary works for the correct and efficient function of the different stages of the exploitation, as well as human accommodation in order to satisfy everyone´s needs. ​

D - Grinding Plant; ​

(Ball Mill) (Jachal City) fines and ultra fines concentration. ​

D1 – Fine Concentration ​

The fine grinding is carried out in ball mills in a close circuit to pass lately to the fine concentration stage, which will be carried out in gravimetric concentration tables. ​ The concentration tables are devices of gravimetric concentration with laminar flux over an inclined surface. Those are mainly the types with vibratory longitudinal movements, where mineral particles difference one from the other forming sashes as a belt (eyebrows), according to its specific weight (and to granulometry). The table with longitudinal vibration movement (vibrating table) is very well known according to its model and size, the tables are used to concentrate fine and ultra-fine minerals with a maximum capacity of 1,5 t/h per unit.


Due to the fact that studies has been performed on an alluvial ( Dr. Lara , Dr. Murillo), the exploration tasks in alluviums will be extended to other alluviums in the property. ​

In its report, the Engineer (in Mines) Raul Basañez evaluates and quantifies the mineral reserves of de alluvium to be exploited. For this, and for a conservative calculation, the Engineer Basañez takes a grade way much lower than the ones informed by Dr. Lara in his report. ​


The camping will be formed by 20 modules: Approximately 10 modules for 20 persons (workers). 5 modules for cooking and space to have lunch/dinner, 3 modules VIP for professionals and visits,1 module for a micro hospital and 1 modulo for offices and communications. It counts with a 300 m2 warehouse with a paved base, an iron structure and columns. There will be also an easement, gas reservoir, etc., specialized personnel (mechanics, mobility maintenance, etc. ​


ENVIRONMENTAL IMPACT studies must be carried out in the exploitation stage, where we will solicit a General Report, a general description of the environment, of the works realized and measures to protect the environment. ​ Also, the operative center, where the elements that are used should be, must be according to legal parameters regarding construction rules from the access traces to the construction of camping and installations. (Water contention pools, fuel, roadsides, toxic residues, latrines and cameras).


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