Qualla: Iron Quadrangle

Iron Quadrangle: Introduction

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Brazil_location_map.svg: NordNordWest derivative work: Виктор В (talk), CC BY-SA 3.0. The rocks in the Iron Quadrangle are 2.5 billion years old. They were laid down on the edge of the São Francisco craton - the ancient geologic heart of southern Brazil - when the atmosphere first filled with enough oxygen to rust the dissolved iron in the oceans and drop it, band by band, onto the seafloor. That ancient sediment became itabirite: a high-grade iron ore striped with quartz and jasper, so pure that impurities were cooked out during later metamorphism. The wealth built from it has paid for cities, shifted Portuguese colonial policy, and - twice in five years - killed hundreds of people in tailings dam collapses.

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Image: Brazil_location_map.svg: NordNordWest derivative work: Виктор В (talk) | CC BY-SA 3.0

Iron Quadrangle: Four Billion Years in Stripes

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Andrevruas, CC BY-SA 3.0. The Iron Quadrangle is a mineral-rich region of roughly 7,000 square kilometers in south-central Minas Gerais, named for its roughly four-sided shape. The ore deposits sit within the Cauê Formation, part of the Minas Supergroup, a sequence of meta-sedimentary rocks deposited betw...

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Image: Andrevruas | CC BY-SA 3.0

Iron Quadrangle: The Gold Rush That Moved an Empire

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Marina Campos Vinhal, CC BY 2.0. European settlers first learned of the region's mineral wealth in 1690. Diamonds followed not long after. The Portuguese crown imposed the *quinto* - a one-fifth tax on production - and the Brazilian Gold Rush began in earnest, running from the late 17th century through the late ...

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Image: Marina Campos Vinhal | CC BY 2.0

Iron Quadrangle: Belo Horizonte and the Modern Quadrangle

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Edson Hwang - User: (WT-shared) Edsonh at wts wikivoyage, CC BY-SA 3.0. Today more than four million people live in the Iron Quadrangle. Belo Horizonte - planned in the 1890s to be a modern replacement for the colonial state capital at Ouro Preto - is the regional economic hub, processing most of the gem and mineral wealth that still flows from the s...

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Image: Edson Hwang - User: (WT-shared) Edsonh at wts wikivoyage | CC BY-SA 3.0

Iron Quadrangle: Mariana, 2015

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Andre Oliveira, CC BY 2.0. On 5 November 2015, the Fundão tailings dam at the Germano mining complex near Mariana collapsed. Tailings dams hold mining waste - slurry of water, sediment, and crushed rock left over after ore is extracted - behind earthen walls. When Fundão failed, approximately 60 million cu...

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Image: Andre Oliveira | CC BY 2.0

Iron Quadrangle: Brumadinho, 2019

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit James St. John, CC BY 2.0. Three years and two months later, on 25 January 2019, Dam I at the Córrego do Feijão iron mine collapsed near the town of Brumadinho. This time 270 people died. Most of them were Vale employees eating lunch at the company cafeteria when the wave of tailings hit. Surrounding agric...

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Image: James St. John | CC BY 2.0