Piedras Blancas deposit, Cerro Quico, El Sacrificio, La Cocha Department, Tucumán Province, Argentinai

Regional Level Types
Piedras Blancas deposit	Deposit
Cerro Quico	Mountain
El Sacrificio	Municipality
La Cocha Department	Department
Tucumán Province	Province
Argentina	Country

Wolframite deposit associated with a 400 meters x 100 meters body of quartz hosted in granite. Located in the Aconquija mountains (1,950 m elevation).

Cerro Quico, which presents the Wolframite, lies to the southwest of the province, within the 13 sheet and "Villa Alberdi" in the geological-economical Charter of the Argentina Republic, erected by the National Directorate of mining. It belongs to the cord of the Aconquija. The mineral appears on the South-East part of this hill.
Access to place is hampered even today by the lack of roads, since there from the levelling dam of San Ignacio to continue on horseback, by paths, for two hours, which are in a bad state of conservation.
The geology of the area is represented by metamorphic rocks with contribution of igneous material and intrusive rocks. The crystalline basement is characterized by the large number of rocks of mixture containing. It's quartz phyllite, micacitas, migmatitas, schists, etc...
There are also bodies and granitic dikes, apart from the fine injection, which is consistent with the schistosity. It is also necessary to include the body of quartz that appears in the southern part of the Quico Hill within this complex of injection.
Wolframite is present in radial guides or shaped mass, disseminated in the mass of quartz and in the vicinity of the contact of the quartz with granite, usually forming nests with a somewhat irregular distribution, as he was evident as a result of the few tasks carried out.
The Quartz is the main gangue and appears in a massive way in the body, which stands on the surface as a white prominence with an extension of about 400 meters long and 150 meters wide and with a North-South direction.
In the mineralized zone, it is possible to observe the presence of idiomorphic quartz crystals hyaline of regular size, having found copies up to 30 centimetres long, as well as smoked quartz and white mica. Also found diffuser quartz crystals, opalized quartz, iron oxides, manganese Oxides, Tungstite, copper minerals, opal, chalcedony.
The Wolframite occurs forming eyes or nests with crystals of more than 6 centimetres long and also is radioactive. Chemical analysis of samples of the site was conducted in the laboratories of the National Commission of atomic energy in Buenos Aires, throwing the following tenors 0.008 to 0.07 U3O8 g%g and Th 0.0052 g%g.
Genetically and Prima Facie it can be considered mineralization formed under hydrothermal conditions of medium to low temperature for primary minerals, whereas the Association of Wolframite with intrusion zone Granite-Quartz no doubt.
Other smaller bodies of Quartz are observable in the region.

The existing mineralization consists of the Association of quartz - wolframite - hübnerite - fluorite - Hematite - limonite - pyrolusite - Malachite - tungstite (ochre of tungsten), according to the paragenetic order studied in cuts polished by Chomnales (1963).
On microscopic examination, there are few Hübnerite proportions, ochre of tungsten, fluorite, hematite, limonite and Malachite, according to R. Chomnales (1963), and uncover for the extraction of these minerals is performed. On the mineralogical composition of Piedras Blancas, X-ray, microscopic and chemical determinations have been especially in areas of blasting material.
Determinations made by Porto and Diaz Taddei (1985), have recognized other mineral not quoted above, which identified it is as Powellite crystals subhedral of green, greyish to bluish, translucent, medium hardness. Sometimes also occur in parallel associations of base square dipyramid. According to the obtained density of 4.2 (± 0.5), the anion of this mineral composition can contain a partial substitution of wolframite isomorphous. Their habit is bipyramidal and usually with striations on their faces. Scattered is located in quartz being optically single positive. By observations with UV source, these sections show that this mineral is fluorescent, coloured yellowish clear, impure, and scores which seem also the mineral mass to the filling of thin vein penetrations diffuse.

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References