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The Comco operation demonstrates that a heap leach with fine crushing and grinding can be a successful alternative to more conventional agitated leaching. Comco is possibly going to the extreme by including grinding, however, the general trend in heap leaching is to crush finer for better recovery. Newer crushing technology makes fine crushing possible and many times the increased recovery justifies the additional costs., The Comco operation demonstrates that a heap leach with fine crushing and grinding can be a successful alternative to more conventional agitated leaching. Comco is possibly going to the extreme by including grinding, however, the general trend in heap leaching is to crush finer for better recovery. Newer crushing technology makes fine crushing possible and many times the increased recovery justifies the additional costs.

Appartient à l’ensemble documentaire : AnvilAmS

Échelle(s) : [Ca 1:44 400 000], Référence bibliographique : 9000:2

The paper describes five major ore deposits of the eastern Andes of Central Bolivia, the Sn deposits of Llallagua, Huanuni and Morococala, and the Sn-Ag deposits of Potosi and Oruro., 1 bib., The paper describes five major ore deposits of the eastern Andes of Central Bolivia, the Sn deposits of Llallagua, Huanuni and Morococala, and the Sn-Ag deposits of Potosi and Oruro.

In central and southern Bolivia the tin deposits are complex vein systems associated with near-surface stocks and subvolcanic eruptive complexe. The ages of these fall into two groups. A northern group extending as far south as the Kari-Kari batholith near Potosi, ranges in age from 23 to 20 million years. A southern group includes the Cerro Rico stock at Potosi and the mineralised eruptive complexes of the Quechisla region which give Upper Miocene ages ranging from 17 to 12 million years. Igneous activity within the tin belt took place as a series of relatively discrete pulse, with a general southward shift with time. The north to south zonation of the metals with tin in the south, is not consistently dependent on the age of the associated igneous rocks and appears to be primarily related to the depth at which the deposits were formed and hence to the regional erosion level, rather than to changes in the geochemistry of the magmas with time or space., In central and southern Bolivia the tin deposits are complex vein systems associated with near-surface stocks and subvolcanic eruptive complexe. The ages of these fall into two groups. A northern group extending as far south as the Kari-Kari batholith near Potosi, ranges in age from 23 to 20 million years. A southern group includes the Cerro Rico stock at Potosi and the mineralised eruptive complexes of the Quechisla region which give Upper Miocene ages ranging from 17 to 12 million years. Igneous activity within the tin belt took place as a series of relatively discrete pulse, with a general southward shift with time. The north to south zonation of the metals with tin in the south, is not consistently dependent on the age of the associated igneous rocks and appears to be primarily related to the depth at which the deposits were formed and hence to the regional erosion level, rather than to changes in the geochemistry of the magmas with time or space.

The mine, to date, has produced over 450 000 t of ore. Chromite mineralisation occurs within the mantle-crust transition zone characterised by the interlayering of ultramafic and gabbroic rocks. Sulphide-free ores at the mine represent more than 80 vol% of the chromitites and are similar to podiform chromitites. The sulphide-rich ores are related to the intrusion of dykes of pegmatitic gabbro, and the sulphide can be up to 60 wt% of the rock. Mineralogical and chemical data indicate that sulphide assemblages formed from residual magmatic sulphide-rich melts segregated from the parental volatile-rich pegmatitic gabbro melts. Discordant pegmatitic gabbro dykes could be the result of fractional crystallisation of strongly hydrated melts derived from the dehydration of the subducting slab and small-scale reactions with the mantle wedge., The mine, to date, has produced over 450 000 t of ore. Chromite mineralisation occurs within the mantle-crust transition zone characterised by the interlayering of ultramafic and gabbroic rocks. Sulphide-free ores at the mine represent more than 80 vol% of the chromitites and are similar to podiform chromitites. The sulphide-rich ores are related to the intrusion of dykes of pegmatitic gabbro, and the sulphide can be up to 60 wt% of the rock. Mineralogical and chemical data indicate that sulphide assemblages formed from residual magmatic sulphide-rich melts segregated from the parental volatile-rich pegmatitic gabbro melts. Discordant pegmatitic gabbro dykes could be the result of fractional crystallisation of strongly hydrated melts derived from the dehydration of the subducting slab and small-scale reactions with the mantle wedge.

The deposit, in New South Wales, lies within the upper parts of the Broken Hill Group of the Early to Middle Proterozoic Willyama Supergroup. The Potosi shear is a strongly foliated retrogressed shear characterised by abundant sericite. Mineralisation consists of coarse grained, black, Fe-rich sphalerite (marmatite) as the dominant sulphide and occurs in four main types: stringer to submassive medium to coarse marmatite, massive brown to black marmatite with some pebbly ore texture, varying proportions of disseminated galena-chalcopyrite mineralisation with fine veinlets and stringers of marmatite with subordinate galena, and stringer marmatite with negligible galena in blue quartz psammite. Ore is currently being mined from an open pit at a planned production rate of 200 000 t/a. Proved and probable ore reserves are 1 100 000 t grading 2.1% Pb, 8.9% Zn and 26 g/t Ag in the top 90 m., The deposit, in New South Wales, lies within the upper parts of the Broken Hill Group of the Early to Middle Proterozoic Willyama Supergroup. The Potosi shear is a strongly foliated retrogressed shear characterised by abundant sericite. Mineralisation consists of coarse grained, black, Fe-rich sphalerite (marmatite) as the dominant sulphide and occurs in four main types: stringer to submassive medium to coarse marmatite, massive brown to black marmatite with some pebbly ore texture, varying proportions of disseminated galena-chalcopyrite mineralisation with fine veinlets and stringers of marmatite with subordinate galena, and stringer marmatite with negligible galena in blue quartz psammite. Ore is currently being mined from an open pit at a planned production rate of 200 000 t/a. Proved and probable ore reserves are 1 100 000 t grading 2.1% Pb, 8.9% Zn and 26 g/t Ag in the top 90 m.

The Santa Eulalia mining district, covering approximately 30 km2 is located 25 km east of the town of Chihuahua in the Sierra Santo Domingo. It is divided into two mineralised zones: the East Field (San Antonio Mine) and the West Field (Buena Tierra and Potosi Mines). The orebodies are principally chimneys and mantos, consisting of minor filling and replacement along fractures and disseminated minerals in tactites. The local geology, mineral deposits and economic geology of the area are described., The Santa Eulalia mining district, covering approximately 30 km2 is located 25 km east of the town of Chihuahua in the Sierra Santo Domingo. It is divided into two mineralised zones: the East Field (San Antonio Mine) and the West Field (Buena Tierra and Potosi Mines). The orebodies are principally chimneys and mantos, consisting of minor filling and replacement along fractures and disseminated minerals in tactites. The local geology, mineral deposits and economic geology of the area are described.

The Late Miocene San Cristobal deposit occurs in an intermediate-composition volcanic centre in southern Bolivia's Altiplano region. Apex Silver Mines is currently developing the prospect, which has been worked since Spanish times, into a series of open pits which will eventually merge. Proven and probable reserves are 240 000 000 tonnes of ore grading 2 oz/tonne Ag, 1.67% Zn and 0.58% Pb. The deposit is the product of syngenetic and epigenetic mineralisation with low- and high-sulphidation characteristics. The area of the deposit is characterised by barren dacitic ring fracture domes, mineralised resurgent rhyodacite domes, strongly altered and mineralised tuffaceous lacustrine sedimentary rocks, and an extensive crystal-lithic tuff apron. The orebody is hosted by intra-cauldron sedimentary rocks and breccias. Fluid inclusions suggest that silver, lead and zinc were transported as chloride complexes and precipitated by cooling at 170-215 degrees C. Silver associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH., The Late Miocene San Cristobal deposit occurs in an intermediate-composition volcanic centre in southern Bolivia's Altiplano region. Apex Silver Mines is currently developing the prospect, which has been worked since Spanish times, into a series of open pits which will eventually merge. Proven and probable reserves are 240 000 000 tonnes of ore grading 2 oz/tonne Ag, 1.67% Zn and 0.58% Pb. The deposit is the product of syngenetic and epigenetic mineralisation with low- and high-sulphidation characteristics. The area of the deposit is characterised by barren dacitic ring fracture domes, mineralised resurgent rhyodacite domes, strongly altered and mineralised tuffaceous lacustrine sedimentary rocks, and an extensive crystal-lithic tuff apron. The orebody is hosted by intra-cauldron sedimentary rocks and breccias. Fluid inclusions suggest that silver, lead and zinc were transported as chloride complexes and precipitated by cooling at 170-215 degrees C. Silver associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH.

The historical importance of the Cerro is reflected by its central place in Bolivia's coat of arms. Silver from the Rich Mountain helped make Spain a great power in the 16th century, and a century after independence the boom in industrial demand for tin resulted in investment to exploit the deeper lodes. Nationalised after the 1952 revolution, the mine became run down and after the 1985 fall in tin prices and the election of a reformist government, it was forced to close in 1993. Two 1 000 t/d heap leaching projects are treating dumps, which total 3 000 000 t grading 213 g/t Ag and 0.1-0.25% Sn. In the oxidised upper reaches of the Cerro, hard-rock reserves of 142 000 000 t grading 174 g/t Ag and 0.1-0.25% Sn have been established, but plans for underground mining with backfilling are opposed by 37 mining co-operatives and thousands of peasants that work the hill. An alternative is to develop the area as a museum., The historical importance of the Cerro is reflected by its central place in Bolivia's coat of arms. Silver from the Rich Mountain helped make Spain a great power in the 16th century, and a century after independence the boom in industrial demand for tin resulted in investment to exploit the deeper lodes. Nationalised after the 1952 revolution, the mine became run down and after the 1985 fall in tin prices and the election of a reformist government, it was forced to close in 1993. Two 1 000 t/d heap leaching projects are treating dumps, which total 3 000 000 t grading 213 g/t Ag and 0.1-0.25% Sn. In the oxidised upper reaches of the Cerro, hard-rock reserves of 142 000 000 t grading 174 g/t Ag and 0.1-0.25% Sn have been established, but plans for underground mining with backfilling are opposed by 37 mining co-operatives and thousands of peasants that work the hill. An alternative is to develop the area as a museum.

Pb isotope ratios of ores and igneous rocks from the San Cristobal silver-zinc deposit and from Palaeozoic and Cretaceous sedimentary rocks are compared with published data on high-grade Middle Proterozoic metamorphic basement rocks. The easily leachable Pb is much less radiogenic than Pb in the whole sedimentary rocks, but both are too radiogenic to have been major sources of Pb for San Cristobal. Pb isotope ratios of ores from the Pulcayo polymetallic district and the giant Potosi silver-tin-base metal deposit are similar to each other and lie within the range of the whole sedimentary rocks, but leaching of Pb from the sedimentary rocks cannot explain the compositions of these ores and the isotopic composition of the Potosi ores argues against mixing of Pb from diverse sources in the hydrothermal system. Pb from the sedimentary rocks may have been assimilated into the magma. In the San Cristobal region, the degree of incorporation of ore metals from the metamorphic basement appears to have depended on the timing and/or location of the mineralising event., Pb isotope ratios of ores and igneous rocks from the San Cristobal silver-zinc deposit and from Palaeozoic and Cretaceous sedimentary rocks are compared with published data on high-grade Middle Proterozoic metamorphic basement rocks. The easily leachable Pb is much less radiogenic than Pb in the whole sedimentary rocks, but both are too radiogenic to have been major sources of Pb for San Cristobal. Pb isotope ratios of ores from the Pulcayo polymetallic district and the giant Potosi silver-tin-base metal deposit are similar to each other and lie within the range of the whole sedimentary rocks, but leaching of Pb from the sedimentary rocks cannot explain the compositions of these ores and the isotopic composition of the Potosi ores argues against mixing of Pb from diverse sources in the hydrothermal system. Pb from the sedimentary rocks may have been assimilated into the magma. In the San Cristobal region, the degree of incorporation of ore metals from the metamorphic basement appears to have depended on the timing and/or location of the mineralising event.

Pallacos are found on the flanks of the Cerro Rico, the world's largest silver deposit. Fundamentally, pallacos are gravels whose clasts contain sufficient disseminated silver to be bulk-minable. The Ag-bearing clasts originate from the summit of Cerro Rico and are composed of dacite porphyry or air-fall tuffs or arkosic sandstones of the Caracoles Formation that have been altered to vuggy silica or jasperoid. Analysis of facies, bedforms, depositional textures, and clast sizes and percentages suggests that there are two types of pallaco, each with a different despositional mechanism. The Huacajchi type formed from multiple flows of water-transported debris while the Potosina type is interpreted as catastrophic landslides., Pallacos are found on the flanks of the Cerro Rico, the world's largest silver deposit. Fundamentally, pallacos are gravels whose clasts contain sufficient disseminated silver to be bulk-minable. The Ag-bearing clasts originate from the summit of Cerro Rico and are composed of dacite porphyry or air-fall tuffs or arkosic sandstones of the Caracoles Formation that have been altered to vuggy silica or jasperoid. Analysis of facies, bedforms, depositional textures, and clast sizes and percentages suggests that there are two types of pallaco, each with a different despositional mechanism. The Huacajchi type formed from multiple flows of water-transported debris while the Potosina type is interpreted as catastrophic landslides.

Experiments were carried out using acid mine drainage (AMD) from three abandoned adits that drain active mining zones of the Cerro Rico silver deposit, as well as raw municipal wastewater from the adjacent city of Potosi and locally available limestone. Alkalinity production, acidity neutralisation and metal removal were studied using cubitainers for incubation of AMD in the presence of limestone, a 1:1 mix of AMD and municipal wastewater and a 1:1 mix of AMD and wastewater in the presence of limestone. Mixing AMD with wastewater had relatively little effect on the final alkalinity achieved by limestone dissolution. Dissolved concentrations of Ag, Al, As, Cd, Cr, Fe, Pb, Sb, Se, Sn, V and Zn were reduced by AMD and wastewater incubation, with particularly efficient As removal. AMD mixed and unmixed with wastewater then incubated with limestone generally reduced REE concentrations, but Pr and Nd concentrations increased under some limestone exposures. Incubation with wastewater alone generally reduced dissolved concentrations of REE, but La, Pr, Eu and Nd concentrations increased. The results indicate that cubitainer incubations have broader application than previously exploited and that passive treatment can be expanded to target more constituents of interest than traditionally applied. Co-treatment of AMD with wastewater is a promising new application of passive treatment. Although locally sourced limestone can increase final alkalinity up to 397 mg/l as CaCO3, it is a potential source for Mn and a few other possibly undesirable elements., Experiments were carried out using acid mine drainage (AMD) from three abandoned adits that drain active mining zones of the Cerro Rico silver deposit, as well as raw municipal wastewater from the adjacent city of Potosi and locally available limestone. Alkalinity production, acidity neutralisation and metal removal were studied using cubitainers for incubation of AMD in the presence of limestone, a 1:1 mix of AMD and municipal wastewater and a 1:1 mix of AMD and wastewater in the presence of limestone. Mixing AMD with wastewater had relatively little effect on the final alkalinity achieved by limestone dissolution. Dissolved concentrations of Ag, Al, As, Cd, Cr, Fe, Pb, Sb, Se, Sn, V and Zn were reduced by AMD and wastewater incubation, with particularly efficient As removal. AMD mixed and unmixed with wastewater then incubated with limestone generally reduced REE concentrations, but Pr and Nd concentrations increased under some limestone exposures. Incubation with wastewater alone generally reduced dissolved concentrations of REE, but La, Pr, Eu and Nd concentrations increased. The results indicate that cubitainer incubations have broader application than previously exploited and that passive treatment can be expanded to target more constituents of interest than traditionally applied. Co-treatment of AMD with wastewater is a promising new application of passive treatment. Although locally sourced limestone can increase final alkalinity up to 397 mg/l as CaCO3, it is a potential source for Mn and a few other possibly undesirable elements.

Mining operations in the country are reviewed against the background of possible further nationalisation of the industry, following the seizure by the government of the Vinto tin smelter in 2007. In Potosi, Apex Silver Mines and Sumitomo began production at the San Cristobal Zn- Pb-Ag mine and Coeur d'Alene Mines started Ag production at the San Bartolome mine. New projects include South America Silver's Ag-In discovery at the Malku Khota project and Eaglecrest Exploration's San Simon Au project., Mining operations in the country are reviewed against the background of possible further nationalisation of the industry, following the seizure by the government of the Vinto tin smelter in 2007. In Potosi, Apex Silver Mines and Sumitomo began production at the San Cristobal Zn- Pb-Ag mine and Coeur d'Alene Mines started Ag production at the San Bartolome mine. New projects include South America Silver's Ag-In discovery at the Malku Khota project and Eaglecrest Exploration's San Simon Au project.

Potosi is a well known historical mining site where mining activity centred on the Cerro Rico, an impressive mount formed by rhyolitic rocks affected by intensive hydrothermal alteration and hosting a complex vein deposit of mainly Ag and Sn minerals. From the 16th century to 1850 the main ores were Ag minerals and from 1850, when the Ag ores were exhausted, activity centered on Sn minerals. During the first stage, Ag minerals were treated by amalgamation using the 'metodo de patio' with Hg and other compounds as metallurgical agents, releasing large quantities of Hg to the local environment. This work was carried out at up to 32 Ingenios or milling and Hg processing facilities, now in ruins, located next to streams so as to have the water and mechanical energy needed for the process. Results from a mainly vehicle-based atomic absorption spectrometer study with high-frequency modulation of light polarisation show very low Hg vapour concentrations of occasionally more than 4 ng/m3 in the area, maximum 31 ng/m3 in the town area, and an average of 5.5 ng/m3. Detailed surveys at the Ingenios demonstrated low Hg concentrations in these facilities but excavation of the topsoil caused a release of elemental vapour reaching over 3 000 ng/m3. Biological and physicochemical processes may have caused the transformation of metallic Hg in the soil to mineral phases cinnabar/metacinnabar and/or schuetteite in reactions mediated by formation of methylmercury., Potosi is a well known historical mining site where mining activity centred on the Cerro Rico, an impressive mount formed by rhyolitic rocks affected by intensive hydrothermal alteration and hosting a complex vein deposit of mainly Ag and Sn minerals. From the 16th century to 1850 the main ores were Ag minerals and from 1850, when the Ag ores were exhausted, activity centered on Sn minerals. During the first stage, Ag minerals were treated by amalgamation using the 'metodo de patio' with Hg and other compounds as metallurgical agents, releasing large quantities of Hg to the local environment. This work was carried out at up to 32 Ingenios or milling and Hg processing facilities, now in ruins, located next to streams so as to have the water and mechanical energy needed for the process. Results from a mainly vehicle-based atomic absorption spectrometer study with high-frequency modulation of light polarisation show very low Hg vapour concentrations of occasionally more than 4 ng/m3 in the area, maximum 31 ng/m3 in the town area, and an average of 5.5 ng/m3. Detailed surveys at the Ingenios demonstrated low Hg concentrations in these facilities but excavation of the topsoil caused a release of elemental vapour reaching over 3 000 ng/m3. Biological and physicochemical processes may have caused the transformation of metallic Hg in the soil to mineral phases cinnabar/metacinnabar and/or schuetteite in reactions mediated by formation of methylmercury.

A microcosm-scale, three-stage batch reactor system was constructed to test the viability of the passive co-treatment of Zn-rich acid mine drainage (AMD) and raw municipal wastewater. AMD from an abandoned adit on Cerro Rico de Potosi with a pH of 3.58 and acidity of 1 080 mg/l as CaCO3 equivalent containing 12, 68, 17, and 550 mg/l of dissolved Al, Fe, Mn, and Zn respectively was mixed at a 5:1 ratio with raw municipal wastewater from Potosi, Bolivia with 5.6 and 38 mg/l nitrate and phosphate respectively. Compared with the influent mix and accounting for dilution, dissolved Al, Fe, Mn, and Zn concentrations were decreased by 99.7%, 99.9%, 4.5%, and 33.9% respectively. PHREEQC geochemical modelling indicated the formation of various solid-phase metallic complexes. Nitrification occurred despite inhibitory Zn concentrations. Phosphate was decreased to below detection limits and pH increased to 7.06. The study revealed the feasibility of passively co-treatming non-synthetic AMD and raw unscreened municipal wastewater at relatively low ambient temperatures of 8.2-10.3 degrees C., A microcosm-scale, three-stage batch reactor system was constructed to test the viability of the passive co-treatment of Zn-rich acid mine drainage (AMD) and raw municipal wastewater. AMD from an abandoned adit on Cerro Rico de Potosi with a pH of 3.58 and acidity of 1 080 mg/l as CaCO3 equivalent containing 12, 68, 17, and 550 mg/l of dissolved Al, Fe, Mn, and Zn respectively was mixed at a 5:1 ratio with raw municipal wastewater from Potosi, Bolivia with 5.6 and 38 mg/l nitrate and phosphate respectively. Compared with the influent mix and accounting for dilution, dissolved Al, Fe, Mn, and Zn concentrations were decreased by 99.7%, 99.9%, 4.5%, and 33.9% respectively. PHREEQC geochemical modelling indicated the formation of various solid-phase metallic complexes. Nitrification occurred despite inhibitory Zn concentrations. Phosphate was decreased to below detection limits and pH increased to 7.06. The study revealed the feasibility of passively co-treatming non-synthetic AMD and raw unscreened municipal wastewater at relatively low ambient temperatures of 8.2-10.3 degrees C.

The stibnite mineralisation spans the entire range between compression-related mesothermal shear zone-hosted and extension-related epithermal acid sulphate-type environments. Deposits hosted by shear zones can be interpreted as a subgroup of greywacke- or turbidite-hosted mesothermal gold lodes in late Proterozoic and Palaeozoic sequences of back-arc basins, which are dominated by sediments and lack thick volcanic components. The Sb accumulated in vein-type deposits of this crustal section was obviously preconcentrated in the host environment. The acid sulphate-type mineralisation is a component of epithermal high-sulphidation gold deposits which originated from subduction-related magmatism., The stibnite mineralisation spans the entire range between compression-related mesothermal shear zone-hosted and extension-related epithermal acid sulphate-type environments. Deposits hosted by shear zones can be interpreted as a subgroup of greywacke- or turbidite-hosted mesothermal gold lodes in late Proterozoic and Palaeozoic sequences of back-arc basins, which are dominated by sediments and lack thick volcanic components. The Sb accumulated in vein-type deposits of this crustal section was obviously preconcentrated in the host environment. The acid sulphate-type mineralisation is a component of epithermal high-sulphidation gold deposits which originated from subduction-related magmatism.

The area known as the Ribera de la Vera Cruz, where the silver ores of Bolivia's Cerro Potosi were processed in the period between the start of mining in 1544 and the founding of the Republic in 1825, can be taken as having extended from the lake of San Sebastien as far as Cantumarca. Estimates of total installed capacity are 2 112 t/a in 1576, 85 536 t/a in 1582 (49 watermills, 81 stamps and 548 hammers), 115 104 t/a in 1633, 60 192 t/a in 1692, 71 808 t/a in 1781 and 82 368 t/a in 1790. Silver production in Potosi rose from under 40 t/a in the early 1570s to over 200 t/a in the early 1590s, then declined steadily to under 40 t/a around 1725, rose above 80 t/a in the 1780s and declined again thereafter. The amalgamation process was introduced to Potosi at the end of 1572 by D. Francisco de Toledo, who proposed the construction of water-powered plants fed by a system of lakes and canals. The period 1572-1577 was one of feverish activity, as plants powered by human, animal or water power were built. The following are described in detail and their weekly production data tabulated for Jan./Feb. or Feb./Mar. 1790: San Marcos, San Diego, La Concepcion, Los Urives, Los Gambartes, Cuti and Dolores., The area known as the Ribera de la Vera Cruz, where the silver ores of Bolivia's Cerro Potosi were processed in the period between the start of mining in 1544 and the founding of the Republic in 1825, can be taken as having extended from the lake of San Sebastien as far as Cantumarca. Estimates of total installed capacity are 2 112 t/a in 1576, 85 536 t/a in 1582 (49 watermills, 81 stamps and 548 hammers), 115 104 t/a in 1633, 60 192 t/a in 1692, 71 808 t/a in 1781 and 82 368 t/a in 1790. Silver production in Potosi rose from under 40 t/a in the early 1570s to over 200 t/a in the early 1590s, then declined steadily to under 40 t/a around 1725, rose above 80 t/a in the 1780s and declined again thereafter. The amalgamation process was introduced to Potosi at the end of 1572 by D. Francisco de Toledo, who proposed the construction of water-powered plants fed by a system of lakes and canals. The period 1572-1577 was one of feverish activity, as plants powered by human, animal or water power were built. The following are described in detail and their weekly production data tabulated for Jan./Feb. or Feb./Mar. 1790: San Marcos, San Diego, La Concepcion, Los Urives, Los Gambartes, Cuti and Dolores.

The immense amounts of silver mined in Cerro Rico in the 16th century influenced the entire economy of the Peru Viceroyalty and even changed the European and Spanish economies. The patio or amalgam process for silver extraction was introduced in Potosi in 1573. Indians were forced to work in the mine and the 150 surrounding mills and many thousands died each year, particularly from mercury poisoning. By 1572 the extremely high-grade ore in the upper part of the mountain was largely exhausted. Deeper levels were mined for lower-grade ores in the 19th century and in 1852 many of the mines changed from silver to tin due to low silver prices. The upper zone is still mined by many private companies from claims leased from COMIBOL. COMIBOL's mine is developed up to a depth of 1 150 m from the summit. A museum has been proposed within the mine, with an interpretation centre at the mine entrance., The immense amounts of silver mined in Cerro Rico in the 16th century influenced the entire economy of the Peru Viceroyalty and even changed the European and Spanish economies. The patio or amalgam process for silver extraction was introduced in Potosi in 1573. Indians were forced to work in the mine and the 150 surrounding mills and many thousands died each year, particularly from mercury poisoning. By 1572 the extremely high-grade ore in the upper part of the mountain was largely exhausted. Deeper levels were mined for lower-grade ores in the 19th century and in 1852 many of the mines changed from silver to tin due to low silver prices. The upper zone is still mined by many private companies from claims leased from COMIBOL. COMIBOL's mine is developed up to a depth of 1 150 m from the summit. A museum has been proposed within the mine, with an interpretation centre at the mine entrance.

The rich deposits of Zacatecas in Mexico and Potosi in Bolivia (Alto Peru) were discovered in 1545/46; in both, the direct smelting ores were exhausted in a couple of decades. The Patio process of amalgamation, in which the ore was ground together with mercury, verdigris and common salt by means of a millstone, had originated in Spain and was adapted by Bartolome de Medina to Mexico's silver ores in about 1554 or 1555. By the early 19th century the ores were ground to powder in mills driven by mules, mixed to a paste, sun-dried and laid out in heaps on an amalgamation floor or patio; salt was mixed and trodden in, roasted copper ore and iron sulphate were added, and mercury sprinkled over at about 8 parts mercury to one part by weight of silver in the ore. Silver was won from the amalgam by washing, straining and distillation. At Potosi, where the cold and high altitude necessitated different processes, the Incas smelted ores in guayras or clay furnaces pierced by air vents, placed on the windy hillsides. By 1565 large quantities of unsmeltable ores were accumulating above ground, and in 1570 amalgamation was introduced from Mexico. The Buytron process had as its characteristic modification the use of heat, with the vessels containing ground ore, brine and mercury being placed over furnaces. In 1590 salt and mercury were the only reagents, the use of copper sulphate being discovered in Bolivia in about 1601 and iron filings being mentioned in a tax petition of 1618. In the 1640s 125 mills served the Potosi mines while a further 60 processed ore from other mines., The rich deposits of Zacatecas in Mexico and Potosi in Bolivia (Alto Peru) were discovered in 1545/46; in both, the direct smelting ores were exhausted in a couple of decades. The Patio process of amalgamation, in which the ore was ground together with mercury, verdigris and common salt by means of a millstone, had originated in Spain and was adapted by Bartolome de Medina to Mexico's silver ores in about 1554 or 1555. By the early 19th century the ores were ground to powder in mills driven by mules, mixed to a paste, sun-dried and laid out in heaps on an amalgamation floor or patio; salt was mixed and trodden in, roasted copper ore and iron sulphate were added, and mercury sprinkled over at about 8 parts mercury to one part by weight of silver in the ore. Silver was won from the amalgam by washing, straining and distillation. At Potosi, where the cold and high altitude necessitated different processes, the Incas smelted ores in guayras or clay furnaces pierced by air vents, placed on the windy hillsides. By 1565 large quantities of unsmeltable ores were accumulating above ground, and in 1570 amalgamation was introduced from Mexico. The Buytron process had as its characteristic modification the use of heat, with the vessels containing ground ore, brine and mercury being placed over furnaces. In 1590 salt and mercury were the only reagents, the use of copper sulphate being discovered in Bolivia in about 1601 and iron filings being mentioned in a tax petition of 1618. In the 1640s 125 mills served the Potosi mines while a further 60 processed ore from other mines.

Results of studies of the mode of occurrence, mineral assemblage and paragenesis, chemical composition and x-ray powder diffraction data of samples from the Potosi, Caracota, Huari Huari, Tasna, Chorolque, Animas, Siete Suyos and Tatasi mines are presented., Results of studies of the mode of occurrence, mineral assemblage and paragenesis, chemical composition and x-ray powder diffraction data of samples from the Potosi, Caracota, Huari Huari, Tasna, Chorolque, Animas, Siete Suyos and Tatasi mines are presented.

The Potosi primary tin deposit is an exogreisen body contained within a near vertical breccia pipe, related to a nearby Rondonian tin-granite. The orebody is believed to have formed as a result of volatile concentration (particularly fluorine) beneath an impermeable carapace of the Pedra Branca granite and the subsequent escape of these volatiles along the basement fractures to surface, producing the breccia and tin/tungsten mineralisation., The Potosi primary tin deposit is an exogreisen body contained within a near vertical breccia pipe, related to a nearby Rondonian tin-granite. The orebody is believed to have formed as a result of volatile concentration (particularly fluorine) beneath an impermeable carapace of the Pedra Branca granite and the subsequent escape of these volatiles along the basement fractures to surface, producing the breccia and tin/tungsten mineralisation.

A peculiarity of Bolivian mining by world standards is that nearly all the mines are small. Small groups of workers producing a tonne of tin concentrate a month or less are common. The structure of mining in Bolivia is examined and the current mines operating outlined., A peculiarity of Bolivian mining by world standards is that nearly all the mines are small. Small groups of workers producing a tonne of tin concentrate a month or less are common. The structure of mining in Bolivia is examined and the current mines operating outlined.

RésuméContrairement à ce que suggère le concept universalisant de Patrimoine de l’humanité, dans les faits, le patrimoine n’existe jamais que dans des appropriations et des configurations sociales et historiques particulières. Ces dernières sont elles-mêmes traversées par des clivages qui divisent les populations concernées, à l’heure de définir où commence et où finit l’injonction du patrimoine. En raison de son histoire coloniale, le site minier de Potosi a été déclaré Patrimoine de l’humanité en 1987. L’usage fait de ce titre, par une partie de la population pour s’opposer à sa mise en exploitation massive, et la relégation des enjeux économiques et politiques du débat sont ici l’occasion de s’interroger sur les tensions et les écueils qui surgissent de la confrontation entre la vocation universalisante et publique du patrimoine et les intérêts particuliers des acteurs sur le terrain., The concept of « Mankind Heritage » is universal and abstract. It really exists only in specific social and historical contexts. These contexts give birth to conflicts dividing the population on the size and scope of what must be protected. As a witness of colonial history, the Potosi mine became « Mankind Heritage » in 1987. A sector of the population takes advantage of this prestigious title to refuse a large-scale exploitation of the site, without paying attention to economic and political issues. This example shows tensions and obstacles between local private interests and the universal and public characters of a patrimonial heritage., ResumenContrariamente a lo que sugiere el concepto « universalizador » de « Patrimonio de la Humanidad », en los hechos, el patrimonio solo existe dentro de apropiaciones y configuraciones socio-históricas particulares. Estas se caracterizan por discrepancias que dividen las poblaciones a la hora de definir donde empieza, y donde acaba, la autoridad del patrimonio. Debido a su pasado colonial, el sitio minero de Potosí fue declarado « Patrimonio de la Humanidad » en 1987. Un sector de la población hace uso de ese título para oponerse a la explotación a grán escala de los yacimientos mineros, eliminando, de esta manera, los factores económicos y políticos que están en juego. Esta situación brinda la oportunidad de reflexionar sobre las tensiones y los problemas que surgen de la confrontación entre la vocación universal y pública del patrimonio y los intereses particulares de los actores locales.

Proyecto de vivienda nueva, desarrollada con contenedores marítimos de 3 tipos diferentes de tamaño, bajo el concepto de un hábitat modular que mediante la agrupación de diferentes modelos de contenedores se logre crear tipologías de vivienda para suplir necesidades de la comunidad del este sector. El proyecto se encuentra ubicado en el barrio Potosí, en la localidad de Ciudad Bolívar (Bogotá). Cuenta con un área total (lote) de 6.312m2, donde 480m2 de estos son de espacio publico y zonas verdes del proyecto. Ofrece una solución habitacional de 124 viviendas. El proyecto esta constituido por 5 edificaciones y una zona de espacio publico, donde en el primer nivel (publico) de 3 de estos edificios cuenta con locales comerciales para uso de la comunidad y en 1 de ellos se ubica un área para el desarrollo de talleres de conocimiento dirigido a las personas del sector para el inicio y progreso de las huertas urbanas del barrio. Los tres siguientes niveles son netamente dirigidos al desarrollo de la vivienda (privado) de las personas del sector, donde se manejan 8 tipos diferentes de vivienda que se desarrollan a lo largo de cada edificación. Las huertas urbanas ligadas a la productividad, estarán ubicadas principalmente sobre el borde del barrio (eje ambiental), donde se manejarán distintos tipos de cultivos tales como cebolla, papa, lechuga, entre otros.