History of the Atacama region (Chile): Mining

 Literature: Tres Puntas

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Extracts from the book "Industrial and Historical Review of Mining and Metallurgy in Chile" by Francisco San Roman from 1894. A description of the geology and mining district of Tres Puntas.

Tres Puntas:
Tres Puntas: The calcareous strata continue their invariable course to the NE, leaving traces of their passage in small islets or rockshells attached to the hills or sticking out under the alluvium of the desert until they collide with the southern slopes of two small cords that cross each other in the longitudinal plain and that received from the miners the names of "El Volcán” and “Tres Puntas”.

Object of real or dreamt discoveries, it is already known how he finally came to find those new emporiums of silver. There is no characteristic formation in powerful successions of strata that can be seen in the distance with its smooth and continuous silhouettes, its steep cuts and bands, waving in the heights like wide strips of various colors. In the Chimbero mine it is just a protuberance that appears between the shades of dark red and violated from the earthy sandstones of an ancient, but undetermined time.

A short extension of diorite appears in the south and against it the calcareous layers impregnated with silver ore that constitute that powerful hatchery crash and vanish. Eurythic rocks of different shades occupy the rest of the formation. Extending from there the view over the plain of the arid desert, the attention is fixed on a height that boasts and stands out as an advanced messenger to meet the traveller that goes there from all directions of the south. It is "El Bonete" hill with its dark colors and volcanic appearance, its rough flanks and its rounded summit in the shape that indicates its name.

Curious detail is this fact that we are already left pointed out in Chañarcillo with the volcanic cone of Bandurrias, as a witness of the inner actions of the planet and vigilant of the riches enclosed there; reproduced also in El Bonete de Tres Puntas; repeated later in Caracoles to serve as a guide by the loneliness of that vast wasteland in the same characteristic form in the height that the first explorers called "El Centinela".
From Chimbero, passing between El Volcán and El Bonete, we arrive a few kilometres away from the terrain where the Tres Puntas mines are located, on limestone formation in a undulated plain. In the center, a large stream of a porphyry diorite, a beautiful rock that can be equivalent to Nevada's propylite (1) in the United States, forms a powerful dike from whose outcrops to the surface have been detached pieces that, rounded by the action of time and scattered on the surface, offer the appearance of a field planted with errant blocks that would have been deposited there by the travelling ice of the time (2).

The fantasy of the prospectors (cateadores), impressed with that strange aspect, gave birth in some of them to the idea of some relation of those blocks with the silver hatcheries and they took it into account among their signs indicating wealth. On the slopes of Tres Puntas Hill are the benches of andesite and trachytic tuffs in variegated relation to the calcareous strata, among which stands out a black layer that is a true conglomerate of grifaeas (3) characteristics of the lees blocked by cement impregnated with fossil bitumen that emits an unpleasant smell when hit with the hammer. This fossiliferous layer constitutes a geological horizon that also manifests itself at the foot of the Chañarcillo hill; and in the San Carlos mine, in the Juncal al Carrizo mountain range, it forms one of the boxes of the silver vein.

As in "Ladrillos" can be said of Chimbero, with greater reason, and also of Tres Puntas, that the transition from the upper region of the chlorinated species of silver to that of sulphides, has been even faster and much less extensive depth than in Chañarcillo.  

The "Buena Esperanza" mine and annexed belongings of the Chimbero resulted from the discovery of a crestón of pure silver chloride accompanied by limestone gangs, iron oxides and shallow copper indications of the green colored species.
The discoverers made open-pit and soon discovered that it was not the existence of a single vein but a series of layers or  a series of  grained veins that intersected with each other, enriching itself and distributing mineral currents among successive mantles until considerable distance from the line of intersection, a distance that in parts has exceeded one hundred meters.

No reasoned study or illustrative plans of the geognostic characteristics of that powerful and interesting hatchery have left the administrators of that mine who were so abundant in resources and money without limits to have developed a system of underground explorations that would have been so productive in the days of the current decline. English, French and Germans followed one another there, but none of them have been able to obtain traces that guided us with the criterion of the investigation in that underground labyrinth of deposits in all forms and of labors followed to all the directions of the nautical rose (4).

Eurythic rocks intervene there with calcareous strata in introductory layers, but distributed in an order or according to some mineral content that no one has been careful to find out. In all times there was that sense of mystery, secret assumptions and cloaked saints that the vulgarity and tactical leguleya in the ventilation of lawsuits always opposed the study and general knowledge of the conditions and singularities of each mining seat, which so teaching experience and so useful works of information and consultation could have left us.

In little more than a hundred meters deep, the nomenclature of the mantle of AAs, BBs, and MMs, in the series of metalliferous layers, had exhausted the alphabet of the languages, distinguishing itself with the name of Manto San Juan de Dios, which more than millions pushed in circulation of Chile's public fortune.  

At such shallow depth, nothing was known of the future of that opulent deposit: the vein of Buena Esperanza, in its regular formation and ordinary dimensions of striking and power, was not the object of deep research after the interposition of a stone horse separated it into two groups filled only with the generous carbonate of lime, but without costing benefits; nor were explorations followed in the horizontal on it or on the  the other estructutres as link between the two points, the limestone formation is developed on the hill of the Volcano, in the mine of the same name, and on the other hand in San Pedro Nolasco, in the Republican and in the rich guides of Barcelonesa, with the inseparable green eruptive rock and the metamorphic garnets of Chañarcillo. In Tres Puntas they open the veins on the terrain barely undulating or on the surface, but the stratified formation appears solid in depth.

The eruptive rocks have produced more disturbing and profound accidents there than in Chañarcillo, dragging the veins along their course and dislocating them strongly. Thus, the vein of the  "Juana","Salvadora" and "Al fin Hallada" rises recumbent and sterile against the eastern wall of the dioritic dike; it is enriched when crossing the calcareous stratified formation changing at the same time of direction, it is joined with other filons or veins of calcium carbonate or barium sulfate that enrich it even more, and thus, from one unusual situation to another, the angles that form in its course the shape of a zig-zag..
The thickness of the stratified formation does not seem considerable there, but the works in the Al Fin Hallada sustained the extraordinary production of native silver and pure minerals while it lasted there, without interruption up to 130 vertical meters and in a horizontal stretch that embraced up to 150 meters.

Continue with good expectations of continuity for 170 meters more, at the depths of which a dyke or set of dykes interposed within which, the vein disappears, had no continuation, abandoning the explorations until today and remaining so to solve one of the underground problems most caressed by the faith and constancy of the miners of Copiapo.

Numerous other mines of Tres Puntas, such as "Victoria","Lautaro","San Rafael" and others, all of them rich within the first depths, and carved on veins of different courses and with more or less analogous characters, have also been abandoned without having resolved the doubts of the continuity of their benefits in new sectors. Deposits of another nature, in pits, such as the "Gallofa", and in successions of mantles, such as the "Luz del Pilar", have not been the object of recognitions that could discover new and productive areas of exploitation.

Ascending at a certain height by the slopes of the cordon of the Tres Puntas, was found the mantle that carried the name of "San José", located at the foot of a dioritic hill and which was studied especially by the distinguished geologist engineer Don Lorenzo Sundt during our explorations of the desert of Atacama. It describes there a dislocation of the ground that causes a slippage of hostrock of the mineral layer in a vertical of 40 to 50 meters, producing the consequent discontinuity in the stratification planes and attributes the appearance of the rich native silver condensations that took place there to the interposition of the diorite, within whose rock the sterility of the seams is general.

Los textos originales fueron digitalizados, transformados a ASCII redactados  por Dr. Wolfgang Griem.

Ruins of Tres Puntas in the Atacama Region in 2008
Mining in historical pictures