The story of the San Luis Potosí mines is one of colonialism, extractivism and pollution

People | Communities

By Isabel Rowbotham, Co-Editor in Chief

Published May 4th, 2022

The mines in San Luis Potosí, Mexico, were born out of Spanish colonialism, then eventually abandoned until the 1990s, when a Canadian mining company took over the site. Their presence, however, was controversial and opened a dispute into who truly owns the land. More importantly, the company has left long-lasting effects on the people and the surrounding biodiversity.

Mexico is one of the world leaders in silver production, but extraction activities from the past and present continue to cause environmental disturbances and infringe on the local people's right to a healthy nature.

View of the Cerro de San Pedro Municipality in San Luis Potosí, Mexico. The hill—now deforested—can be seen behind the church, where the Canadian-owned Mineros San Xavier mine (Gold Inc.) operated. | Colectivo Ecologista Jalisco | Flickr

In the last 10 years, the land near San Luis Potosí in the historic silver mining area was found to be contaminated with mercury—another metal used in the amalgamation of silverーand arsenic. Its levels exceed the limits for toxicity in residential areas according to Mexican regulations.

The colonial beginnings of mining in Mexico

Mining extraction in developing countries is often associated with conflict, due to the colonial and imperialist pasts of these countries. Historically, colonial mining started to satisfy the European demand for precious metals, such as silver and gold, which created a mining boom from the 14th century to the 16th century.

In the 1540s, the Spanish crown was lured by the promise of wealth to continue its colonisation of Mexico, all along the Cordillera down to present-day Chile. The main mines under their control were Zacatecas, San Luis Potosí, Pachuca and Guanajuato. By the 1550s, many Spaniards controlled the silver mines for their cheap and simple refinement of silver ore.

By the 18th century, many miners became free workers, namely African slaves and indigenous people, who did not receive wages but were entitled to a share of the ore they cut. Eventually, most areas relied on free labour due to the decline of silver and mercury (used for silver amalgamation) that never recovered.

‘Historically colonial mining started to satisfy the European demand for precious metals such as silver and gold which created a mining boom from the 14th century to the 16th century.’

Present-day situation

Today, the mines of Cerro de San Pedro, rich in silver and gold, are controlled by Minera San Xavier (MSX), a subsidiary of the Canadian mining company New Gold Inc. since 1996.

In 2021, San Luis Potosí was declared the second-largest producer of silver in the country and recently on the 29th of April 2022, local authorities announced the mine was suddenly closed after not meeting legal standards which guaranteed their licence.

Initially, MSX's presence in the area was disputed and met with resistance by Frente Amplio Opositor (Broad Opposition Front or BOF), a Mexican big-tent political party. This includes MSX’s initial attempt to reportedly relocate the entire town and its inhabitants.

An environmentalist protest at the gates of MSX mines. A sign reads ‘Alto! Ecocidio Nacional’ (Stop! National Ecocide). | | Flickr

The mining activity has had a definite impact on environmental degradation and land and water use rights, which did not outweigh whatever limited economic incentive was to gain. Moreover, the legitimacy of MSX's presence was called into question in the 1990s when Mexico hit an economic depression. As explained by Stoltenborg and Boelens, ‘the World Bank, the International Monetary Fund and the Inter-American Development Bank demanded that Mexico adopt neoliberal policies if the country wanted to obtain international credit.’

Among these bodies was the North American Free Trade Agreement (NAFTA), which incentivised the Mexican government to increase private foreign investment and prioritise mining above all else. It also advised changing how land and water, previously protected as non-commodities, are ‘temporarily occupied’ by these foreign companies. This is a process that is also protected by international courts, which superseded national law.

‘The mining activity has had a definite impact on environmental degradation and land and water use rights.’

In 2001, this allowed the American corporation Metalclad to be awarded $16.5 million dollars by NAFTA under international law. Metalclad had plans to install a hazardous waste landfill at the mines of Cerro de San Pedro but their land occupation faced backlash from the local government, who decided to expropriate the property.

The decision under NAFTA’s Chapter 11, Mexico had effectively taken U.S. investors' property and in a shocking event, was forced to pay back damages to Metalclad. This set a precedent of fear which meant no Mexican authority could object or file a complaint against the Canadian mining company and ensured all future permits they required to continue operations (click here to read the full research paper on how MSX has impacted land and water rights).

MSX continued to push for extraction, but in 2004 its permits were annulled after Cerro de San Pedro was recognised as a UNESCO heritage site. Eventually, MSX was given the green light to start operations in 2005, and with that came a water concession for 1.3 million cubic metres per year. Moreover, the company was accused of overusing the drinking water supply designated for a million people, as reported by the BOF.

A wall art reads ‘Si amas la vida, lucha contra la mina’ (If you love life, fight against the mines). Citizens from San Luis Potosí city, not too far from Cerro de San Pedro also opposed mining activities and many have become affected by the pollution. | el mago del mar | Flickr

The activities also included a lixiviation or leaching area for the use of cyanide to dissolve gold and silver particles; a process that requires great amounts of water.

The toxic effects of mining on health

Mining sites, in particular those used for silver mining, are assumed to be contaminated with mercury, as the latter is used in the amalgamation process to produce silver. In 2014, a surveillance study of children living in the Cedral village of San Luis Potosí found their blood samples contained levels of mercury up to 76.8 micrograms per L−1 when the recommendation established by the US Environmental Protection Agency is 5.8 micrograms L−1.

‘There were accused of overusing the drinking water supply designated for a million people.’

As experts look to better understand how this pollution occurs, this discovery opened up the possibility of the chemical transformation of mercury into soluble mercury contaminating the water, air and farming products in the area. The extent of mining pollution is yet to be fully understood, which opens further questions as to the well-being of children currently growing up in these areas.

Another consequence of open-pit mines includes the amount of dust pollution taken in the wind into nearby croplands. The fact seems to be that NAFTA had no obligation to inform farmers about the toxic effects of mining after they are forced to lease their land under the clause for temporary occupancy.

A right to a ‘healthy nature’

These mining projects have undoubtedly impacted the environment, local communities and the economy. One aspect, in particular, is the association between mining and human rights violations.

Such restrictions can affect nature but also the resources, habitat and security for human survival. The right to a ‘healthy nature’ is the subject of many environmental protection policies in several countries.

A protest outside the premises of Minero San Xavier (MSX), also known as Gold Inc. Scenes show a Canadian flag indicating how a foreign company has taken control of the land, next to a man dressed in a colonial Spanish outfit to illustrate the colonial past of the mines. | Colectivo Ecologista Jalisco | Flickr

It is these types of violations in which many developing countries and their people find themselves and which are closely related to extraction activities aimed at enriching first world countries and banks. Just look at the mines of El Cerrejón in La Guajira, Colombia; where mining companies deprived communities of their main source of water.

In 2015, it was announced that the MSX mines would be shutting down and carrying out a rehabilitation process, which includes sterilisation of the lixiviation area and reforestation of the mining pit.

A 2020 report to UN Global Compact laid out MSX’s update on the now 100% reforested pit and a 30% progress on the restoration of the lixiviation area, as well as further plans to remediate their environmental and human rights impact.

Yet despite these promises, a 2021 independent report on the soil composition found evidence of arsenic and other heavy metals still present after years of intensive extraction. After its sudden closure in April 2022, due to failure to produce permits for the use of explosives and blocking a security and environmental protection inspection; it is now uncertain whether the remediation promises will ever be met.

Until the government laws and the NAFTA committee change, mines across the country, such as that of San Luis Potosí, will likely be passed on to their next ‘temporary occupier’, as the world prepares itself for new demand for metals in the green energy revolution.

Featured Image: Source Colectivo Ecologista Jalisco / Movimiento Mesoamericano Contra Model Mineros | Flickr

Brading D.A. and Cross H. E. (1972) Colonial Silver Mining: Mexico and Peru. Hispanic American Historical Review. Volume 52, issue 4, pages 545–579.

Burton T. (1998) ‘The mining towns of San Luis Potosí, Mexico,’ Mexconnect. Available at: [Accessed March 6th, 2022]

Camacho-Garza A., Acevedo-Sandoval O.A., Otazo-Sánchez E.M. et al (2022) Human Rights and Socio-Environmental Conflicts of Mining in Mexico: A Systematic Review. Sustainability. Volume 14, issue 2, page 769.

Cruz Martinez A. (2005) ‘Semarnat y Sedena deben explicar su participación con Minera San Xavier,’ Jornada. Available at: [Accessed March 6th, 2022]

David L. (2021) ‘San Luis Potosí: segundo productor en minería regional para Zinc, Plata y Cobre,’ Lider Empresarial. Available at: [Accessed March 6th, 2022]

Editor Tiempo Minero (2020) ‘Producción minera de plata en México se reduce,’ Camiper. Available at: [Accessed March 6th, 2022]

Instituto Nacional para el Federalismo y el Desarrollo Municipal (2019) ‘3 de noviembre de 1592, se funda la villa de San Luis Mexquitic, hoy San Luis Potosí,’ Gobierno de Mexico. Available at: [Accessed April 20th, 2022]

Kass S.L. and McCarroll J.M. (2000) ‘The 'Metalclad' Decision Under NAFTA's Chapter 11.’ New York Law Journal. Available at: [Accessed April 20th, 2022]

Leura Vicencio A.K., Carrizales Yañez L. & Razo Soto I. (2017) Mercury Pollution Assessment Of Mining Wastes And Soils From Former Silver Amalgamation Area In North-Central Mexico. Rev. Int. Contam. Ambien. Volume 33, Issue 4, pages 655-669.

Lizet Hernández N. (2019) ‘LP, séptimo lugar nacional en industria minera,’ San Luis Universal. Available at: [Accessed March 6th, 2022]

Lizet Hernández N. (2022) ‘Tras años sin permisos y explotación, clausuran minera San Xavier en Cerro de San Pedro, SLP,’ San Luis Universal. Available at: [Accessed May 2nd, 2022]

Martínez-Toledo A., González-Mille D.J., García-Arreola M.E. et al. (2021) Patterns in utilization of carbon sources in soil microbial communities contaminated with mine solid wastes from San Luis Potosi, Mexico, Ecotoxicology and Environmental Safety, Volume 208, number 111493.

Mines and Communities (2004) Mexico: Court Decision Stops San Luis de Potosí Gold Project. Available at: [Accessed March 6th, 2022]

New Gold Minera San Xavier S.A. de C.V. (2020) ‘Cierre Responsable de Mina Acciones, avances y buenas prácticas,’ UN Global Compact. Available at: [Accessed May 2nd, 2022]

Procuraduria Federal de Proteccion al Ambiente (2017) ‘Verifican Semarnat y Profepa Remediación de Sitio Contaminado en Complejo Metalúrgico de Immsa, En S.L.P.’ Gobierno de Mexico. Available at: [Accessed April 20th, 2022]

Shaw M. (2017) ‘Silver mining in Mexico,’ Investing News. Available at: [Accessed March 6th, 2022]

Stoltenborg D. and Boelens R. (2016) Disputes over land and water rights in gold mining: the case of Cerro de San Pedro, Mexico. Water International. Volume 41, Number 3, pages 447-467.

The Metropolitan Museum of Art (2004) ‘Mexico, 1400–1600 A.D.’ In Heilbrunn Timeline of Art History’. Met Museum. Available at:®ion=canm [Accessed March 6th, 2022]

Biomonitoring the environmental effects of silver mining on Mexico’s rivers

Sustainable Leaders | North America

The Wayuu people of the Guajira

People | Communities