The systematic sampling of the pegmatite structures being exposed in the excavated trenches was initiated. This activity was carried out by the mining engineer Hugo Aparicio and three experienced samplers, who complemented and trained the regular personnel of the company. They took 120 samples, from which 90 heavy mineral concentrates were obtained by panning.
Only the colluvial layer of the trenches exposed as an up to 1.5 m thick layer of loose material on top of the pegmatite has been sampled. The material of 5 vertical channel samples (Photo 02) taken in intervals of 1.0 m. was accumulated and processed as a single sample. This overall sample weighted initially on average 50 kg. The material was sieved on site (Photo 03). The -1.0 cm fraction was homogenized, reduced by quartering to a 20 kg sample (Photo 04) and finally transported to a site for panning (Photo 05), where the experienced panner Mario Roca Surubí concentrated the heavy minerals (Photo 06 & 07). The wet concentrate weighted between 80 and 200 gr. It contained mainly the minerals magnetite, tantalite/columbite, garnet, tourmaline and Fe-Mn-oxides. The sterile tailings were composed of quartz, muscovite, some biotite, alkaline feldspar and metamorphic rock fragments (Photo 08).
The concentrates were then shipped to Santa Cruz, where they were dried, the magnetic components of the +0.6 mm grain fraction separated and the minerals classified by use of a binocular. The tantalite/columbite content of the samples was determined roughly by weighting. It reaches up to ¾ kg. tantalite/columbite per ton in the +0,6 mm grain fraction.
It is planed to combine the taken samples in groups for the analyses of Ta, Nb, U, Th, Sn, and W, because it is necessary for an economical appraisal of the pegmatite exploitation, to have knowledge of the Ta/Nb-ratio and the level of radioactive impurities through U and Th.
The actualization and the interpretation of the geological data have been continued in the last weeks. Exploration data from the nineties have been reprocessed with results of the interpretation of satellite images and the exploration work of the last 12 months. Fig.1 shows as an example the topographic survey map of the project area overlain on the TerraColor satellite image. It contains also the location of the pegmatite swarm and the supposed location for the pilot washing plant that will be installed in the next year.
Conclusions
The trenching program has evidenced the presence of a NW/SE striking pegmatite swarm over a distance of 3.4 km. SW/SE and a maximum thickness of 55.0 m. The current sampling confirmed also a tantalite/columbite mineralization over a strike length of 1.1 km between the lines 51-00 SW and 62-00 SW. The field crew found in that area several large tantalite/columbite pieces and crystals in the colluvial overburden weighting up to 250 g. At some places the mineral beryl was observed in fragments of considerable size.
The exploration work evidenced so far that the pegmatite field is related to a several kilometre wide tectonic deformation zone which strikes NW/SE separating two metamorphic rock complexes. Within this zone intensely sheared muscovite schist, banded iron formations and quartzite and intrusive younger granite exist. The pegmatite swarm extends over a distance of 3.4 km, dips approximately 75° SW and is characterized by an intense muscovitization and tourmalinization of the country rock. The structure is characterized in the Johannes concession by strong magnetic, electromagnetic (H.L.E.M.) and induced polarisation (I.P.) anomalies.
Environmental Impact Study
The environmental geologist Hugo Heymann was assigned to begin with the categorisation of the project for the environmental impact study. Therefore, an initial US$ 1,100.-- payment has been carried out.
Planning
On 20.12.2008, the field work will be interrupted due to the Christmas holidays. Until then, the extension of outcropping tantalite/columbite mineralization will be determined. It will be defined next year precisely through parallel running trenches at short intervals, vertical exploration shafts and tunnelling in three dimensions. The excavated material will be treated in a small pilot washing plant to determine metallurgical parameters for a future industrial plant.
The project execution was carried out so far as originally planned both from the time schedule and costs.
Economic & Political Development
The political situation in the country normalized, after the government and the oppositional parties agreed on a new constitution draft. On 25.01.2009, the population will vote in a referendum on this matter.
The economical situation of Bolivia continues to be stable. The exchange rate stands at the end of the month by Bs 7.07 for one US-Dollar.
Price of Tantalite
The Institute for Geosciences and Natural Resources publishes monthly quotations of raw materials, which can be found at http://www.bgr.bund.de. The price for tantalite concentrate averages since May 2008 US$ 81.57 pro kg Ta2O5,CIF Europe (25/40% Basis 30% Ta2O5, max. 0.5% U3O8+ThO2.
Santa Cruz de la Sierra, November 18, 2008
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