The local Valtreixal stratigraphy in the Valtreixal area is dominated by 3 main formations, all of which broadly strike SW-NE, and dip at approximately 80o to the south- east.

a) Schists - Capas de los Montes. Very stratified and transformed by regional metamorphism, with intercalated quartzites, and marked at the base by conglomerates. Thickness approximately 1000m.

b) Quartzites - Peña Goda/Culebra. Alternating with a variety of types and colours of intercalated schists. Thickness approximately 50- 70m.

c) Slates – Pizarras de Luarca. Pelitic series of siliceous slates, phyllites and schists. This formation hosts most of the mineralisation at Valtreixal. High frequency of segregated quartz veins and schist bands sometimes rich in sulphur. Overall thickness approximately 300-600m.

Much of the mineralisation, especially scheelite, is situated away from the quartz veins and appears to be stratabound. Tin, in the form of cassiterite, occurs in and around the quartz veins. The Valtreixal linear mineralised zones appear, in a general sense, to be confined to specific stratigraphic intervals and there appears to be a degree of separation into tin and tungsten zones. Because of the stratabound nature of the mineralised zones within a shale basin some may consider a sedimentary, syngenitic origin for the tungsten mineralisation to be plausible.

The Valtreixal tungsten (scheelite) and tin (cassiterite) mineralisation exhibits two principal modes of occurrence within southeast dipping, weakly schistose Ordovician shale in the Hercynian (Variscan) tectonic belt. Irregular quartz veins cut the moderately steeply southeast dipping shale and may have associated tin and tungsten mineralisation especially where the veins are brecciated and the adjacent wall rock has been altered to sericite schist.

In places it was observed that minor amounts of white kaolin clay had developed by schist alteration. It is notable that mica, probably muscovite coats some surfaces of the glassy quartz fragments and minor open spaces may indicate incipient, vuggy greisen development. It is postulated that originally the quartz veins developed along fractures in the country rocks.

Subsequently, the possible intrusion of a hypothetical granite body at depth provided a heat source to drive a hydrothermal system, brecciating the quartz veins. Any such granitic or other heat source was sufficiently deep so that the shale, seen at Valtreixal, is beyond the granitic metamorphic aureole. Strong hydro- fracturing and concomitant seismic activity may have created temporary weakness along the laminated shale allowing lateral migration of mineralising solutions away from the brecciated veins or other sources for a considerable distance.

The shale is relatively impervious to solution penetration across the bedding by absorbing stress and by yielding more plastically. High pressure fluids may have ruptured many of the rigid quartz veins. The country wall rock adjacent to the brecciated quartz vein is metamorphosed to sericite schist. In general the shale, based on visual and textural features, is considered to be in the low, chloritic metamorphic range.

The mineralisation at Valtreixal can be classified as a complex vein deposit. The tin mineralisation, in the form of cassiterite, is hosted by a mixture of individual veins, veinlets and vein swarms, generally with the same overall dip and dip direction. The distribution and width of veins can be quite erratic within localised areas.

In the absence of geotechnical testwork, actual topographical toes and crest positions have been measured in areas where there are road cuttings or surface excavations for drilling platforms or access purposes. From these measurements, an average face slope angle of 56o was determined. Based on an assumed bench configuration of 10m benches, 4m berms every 2 benches, and 10m wide haul roads (or safety berms), this has given an estimated overall slope angle of approximately 42o. This overall slope angle has therefore been applied in optimisation work.

The majority of the pit design is cut into the west sloping existing hillside. A 10m wide haul road been put into the design with the exit point at the extreme west end, the lowest of point of the optimal pit rim, at an elevation of approximately 870m. This road is used to access lower parts of the design, down towards the lowest point at 820mRL. Access to the eastern, and higher, part of the pit will be gained from temporary access roads from the existing surface on higher benches.

Berms of 4m have been incorporated into the design every 20m vertically. For the extended highwall of the pit up to 1015mRL on the southern and eastern sides of the pit, additional 14m safety berms were put in every 60m vertically.

The overall pit is approximately 700m in length along strike, and 300m wide at its widest point.

Considerable amounts of earthworks have been completed over the past 2 years at Valtreixal, for preparation of drilling platforms and road access purposes. These cuttings have been made in all of the main rock types that will occur inside the pit envelope. Geologists have also had to take bulk samples from underground galleries for metallurgical testing. This experience has indicated that all of the rock types within the Valtreixal pit can be mined by free digging, so drilling and blasting will not be required.

Main benches will be 10m high, with 5m sub- benches in ore, in order to assist with ore/waste discrimination. Grade control will be assisted by the taking of bench face and trench samples, as well as uv lights to assist with the identification of scheelite.

For scheduling purposes in the current study, the pit has been divided into two principal pushbacks, approximately dividing the pit into a west half and an east half. Mining will start in the western (lower) pushback, and then as mining progresses deeper in this pushback, mining will also start on the upper benches of the eastern pushback. Many of these upper benches will be accessible from temporary roads on south-eastern side of the pit.

The beneficiation plant will have a nominal treatment capacity of 500,000 t/year of crude ore. Under normal conditions, the plant will work 24 hours a day, 365 days a year, and so will operate at approximately 58 tph. All of the milling operations will be housed in single steel clad building structure, with an area of approximately 20,000 m2. It is estimated that the electric power required for the Treatment Plant will be approximately 1,500 kW.

The milling operation is envisaged as:

- Crushing, grinding and gravity separation of scheelite and cassiterite into a bulk concentrate;

- Removal of sulphides from the bulk concentrate by flotation;

- Drying and electrostatic separation of the bulk concentrate into scheelite and cassiterite concentrates.

Similar to current milling operations at Los Santos, crushing and grinding operations would like comprise a jaw crusher, cone crushers, followed by a rod mill. Following separation into different size fractions through hydrocyclones, gravity separation is done through spirals and shaking tables.

Mined ore will fed to a jaw crusher from a ROM pad. It is envisaged that separate stockpiles, according to WO3 or Sn content will be developed maintained. The jaw crusher material will produce minus 200mm material.

The material will then be passed through a cylindrical trommel so as to separate clay and very fine material. The next stage will be a one or two stage roller mill, producing minus 5mm material.

The minus 5mm material from the trommel will go through a process of pre-concentration. Test are still being conducted to determine the best dense media or jig arrangement for this. Two process lines will now be created through use of a Reichert spiral classifier, based on a 250 micron split:
- Coarse material for Sn concentration.
- Fine material for WO3 concentration.

The small rod mill will produce material less than 0.5mm, to assist cleaning in the subsequent flotation. The rod mill will not be more than 20 kW, and run at approximately 1 tph.

Two identical circuits will now be used, with successive stages roughing, cleaning and refining. The roughing step will generate a pre-concentrate which will be passed onto the shaking tables). Mixed material will pass through further spirals stages and a hydroclassifier, for more detailed separation.

A discontinuous flotation process will be used to eliminate sulphides that may accompany ore concentrates. This process will be performed on the bulk concentrate from the first concentration step whose particle size was between 250 microns and 5 mm. The rate of discontinuous flotation will not exceed 2 t / hour.

Flotation concentrate will be dried by a rotary drier with direct flame using diesel fuel. Subsequent to drying, the product will be through magnetic separation, for the removal of metallic or ferromagnetic penalizing particles.

Thereafter, the product will pass through an electrostatic separation process. In this case the mineral particles will pass through a charged by induction metal plate, so that the minerals low conductivity (scheelite, WO3) remain adhered to the plate and high conductivity (cassiterite, Sn) are repelled by the plate.

Tailings will be generated at three different points:

1. Steriles between 250 microns and 5 mm, generated in the initial dense media/Jig preconcentration.

2. Sterile less than 1mm, from the gravity concentration spirals.

3. Sterile less than 38 microns (slimes) from the overflow of the hydrocyclones located at the start of gravity concentration circuit.

In the tailings treatment plant, the first two groups will be drained through vibrating screens, arranging and accumulating material on a draining floor to reduce its humidity below 10% for subsequent handling and final transport.

The third group of tailings will first be subjected to settling in with an anionic flocculant. The decanted solids will then pass through a filter press or vacuum filter, to produce material with a humidity below 25%. This material will then be handled along with the thicker dry tailings material. All reclaimed water from tailings treatment will be reused in the gravimetric sorting circuit.

Water will be used extensively during gravimetric classification. It is expected that 600 m3/hour of water flow will be required in the water treatment plant, for reuse in the processing plant. Suspended fines will be settled out in the treatment, so clean overflow can be recirculated back. On the mine site ditches, will collect all surface run-off, which will be collected in settling ponds for reuse or discharge. Two open water tanks, each of 5,000m3 will be installed.