Operation

Basic data. Geology. The operation.

Strategic deposit

Basic data

La Parrilla mine is one of the world’s most important tungsten deposits outside China. The concessions and research permits cover a total area of more than 7,000 hectares.
The plant is already custom-built and has been in operation since the fourth quarter of 2019 with proven efficiency and high recoveries, until March 2022.
It is currently under care & maintenance and has a re-development plan that incorporates investments in new equipment, which will entail significant improvements and the creation of 500 jobs, to be executed once the required permits have been granted from the Junta de Extremadura and the Confederación Hidrográfica del Guadiana.

Strategic minerals

Geology

Tungsten and Tin in Spain W-Sn mineralization at La Parrilla

Metal earth

Tungsten and Tin in Spain

Tungsten (also known as wolfram) and tin are two metals that, from a metallogenic point of view, have many common characteristics and usually appear in association in the so-called W-Sn deposits.

The project is located in the “Iberian Tungsten and Tin Belt”, one of the most important mining areas in the world due to the large number of mining indications. They include a total of 17,000 traces and small tin and wolfram mines, most of which were mined by artisanal methods during the industry’s heyday.

From a geological point of view, these mineralizations are included in the Iberian Massif.

Geological richness

W-Sn mineralization at La Parrilla

The mineralization of La Parrilla belongs to the Schist-Grauvackic Complex (CEG) – (Díez Balda, 1980) of Cambrian-Precambrian age, the result of the Sardian deformation. It is located in a periclinal zone of the El Saltillo anticlinorium formed by greywackes, slates, sandstones, metavulcanites and basic basement rocks.

It is generally disposed in the form of quartz veins, although two other types have been differentiated .

The mineral paragenesis consists mainly of quartz, arsenopyrite and scheelite (W). Cassiterite (Sn), muscovite, tourmaline, chlorite, pyrite and sphalerite are also abundant. Occasionally, wolframite, hematite, apatite, beryl, chalcopyrite, pyrrhotite and grosularia have been observed.

Mineralization is directly related to the veins. However, the distribution of scheelite and cassiterite, ores of the deposit, is irregular with an important “nugget” effect.

Scorodite, marcasite, covellite and limonite have been identified as supergene alteration minerals.

The mineralization (Scheelite+Arsenopyrite+Casiteria) is associated with quartz veins. The distribution of these minerals (ores of the deposit) within them is irregular, with an important “nugget” effect.

Mineralization types

Three different types of mineralization have been differentiated:

QUARTZ VEINS
Main ore of the deposit, the veins have lenticular shapes cutting the CEG, with direction N30-40ºE and average dip SE 45º. Their thickness varies from millimeters to 60 cm and they are usually grouped in mineralized packages.
Scheelite, occurs as idiomorphic crystals in the contact of extensional veins with typical “comb” type textures.
In veins without a clear opening style, mineralization is more irregular in the form of scheelite, cassiterite and arsenopyrite patches.
The veins can be continuous or lenticular (average 10 cm), with irregular and bifurcated shapes. The areas where the density of these is higher, are those considered as ore to feed the treatment plant.
Mineralized veins have been found outside the current exploitation, about 500 m to the NW and in the Cerro de Los Llanillos, 3 km to the N.
The mineralized zones are affected by strong hydrothermal alteration (arsenopyritization, silicification, tourmalinization, chloritization and greissenization) and are associated with contact metamorphism aureoles and a granitic dome.

Irregular quartz bands "cruciform".
They are very irregular structures, with bifurcations and ramifications and lenticular shapes.
The main direction is east-west (E-W), subparallel to the stratification, with subvertical dips.
They are composed mainly of metamorphic quartz with abundant chlorite and may contain pyrite, chalcopyrite, traces of sphalerite and pyrrhotite. Occasionally could contain scheelite and arsenopiryte if they are crossed by Q vein types.
Generally, they have a thickness of 50 to 200 cm, with diffuse contacts with the bedrock.

Disseminated
They are irregular bodies, of variable thickness from millimetric to metric, with strong mineralization and intense metasomatic alteration. These bodies have been interpreted as granite fingers that produce a skarnification of the hostrock.
The scheelite is disseminated, also distinguishing grosularia-andradite garnet, epidote, amphibole and sulfides (pyrite, pyrrhotite and arsenopyrite, chalcopyrite and sphalerite). These zones are generally accompanied by veins of the first type, although their relationship is not clear.

Iberianrs

The operation

Mining operation

The La Parrilla mine is an open pit tungsten and tin deposit with a conventional blast, load and haul operation that is simple to operate and low cost.

Transport and treatment process

The ore is transported a short distance to the ore stockpiles where primary crushing takes place. The waste rock is deposited in the mine dumps.

Concentration plant

After crushing, the ore passes through a conventional gravity concentration plant consisting mainly of wet spirals, shaking tables and magnetic and electrostatic separation. The product is a high quality concentrate produced at low cost.

Strategic location

Connected to the electricity grid and with access to water supply, its location is strategic: only 7 km from the Madrid-Seville highway and a short distance from Atlantic and Mediterranean ports.

Current status and improvement plan

The plant is already built and has proven performance and effectiveness during the 2.5 years it has been in operation. There is a detailed re-development plan that will be executed once the required permits are obtained.

This plan incorporates the improvement of the plant by installing new equipments at various stages of the production process, which will significantly improve the plant’s productivity.