1980s tin rush camps that sprouted and died in months. Thousands of wildcat miners carved up rivers with hydraulic cannons. Mercury poisoning lingers in sediments and people. A gold rush-scale event most have never heard of.
Wilfredor, CC BY-SA 4.0
The Bom Futuro Frenzy
In 1987, a wildcat prospector, or garimpeiro, discovered one of the world's largest deposits of cassiterite (SnO₂) in the Amazonian state of Rondônia. The site, named Bom Futuro ("Good Future"), triggered a massive and chaotic tin rush. Within a year, an estimated 30,000 miners had descended upon the area, transforming the rainforest into a sprawling area of open pits, mud, and makeshift camps. Between 1988 and 1990, their efforts made Brazil the world's top tin producer.
The mining methods were brutally effective and destructive. Garimpeiros used high-pressure water cannons and dredges to blast away riverbanks and topsoil, creating vast pits and washing tons of sediment into the waterways. At the peak of the rush, the Bom Futuro garimpo was a lawless frontier. From 1987 to 1989, the area saw more than ten homicides per week. The boom was short-lived for most. As surface-level deposits were exhausted, large mechanized companies moved in, pushing out the individual miners and leaving behind a scarred environment and settlements.
A Legacy of Silt and Mercury
The environmental cost of the cassiterite rush is measured in cubic meters and micrograms. At Bom Futuro alone, mining operations discharged over 800,000 cubic meters of waste into local streams and rivers every month. This massive siltation choked the river system for a radius of more than 200 kilometers, blocking sunlight, disrupting photosynthesis, and causing widespread imbalances in the aquatic ecosystem.
Although tin mining does not directly use mercury, the garimpeiros often used it to separate gold, a common byproduct found alongside cassiterite. This liquid mercury entered the environment, where bacteria convert it into highly toxic methylmercury. This compound accumulates in the food chain, reaching dangerous concentrations in fish, a primary food source for local and indigenous populations. Studies in the broader Amazon region have found mercury levels in some communities far exceeding the safe limits established by the World Health Organization. The toxic metal persists in river sediments today, a contaminant from a temporary rush for wealth.
💡Fun Facts
The Bom Futuro deposit was discovered by a lone prospector who spotted the glistening tin ore in the roots of a felled tree.
During its peak, the Bom Futuro mine produced 75,000 metric tons of tin ore in just four years.
Cassiterite, the primary ore of tin, is often called "black gold" and is important for producing solder, solar panels, and lithium-ion batteries.
The informal miners, known as *garimpeiros*, produced 60% of all cassiterite in Brazil in 1990.
This is an open landscape with former mining sites, not a formal tourist attraction. It is accessible anytime.
Admission
Free
Accessibility
The region is remote and access to specific former mining camps can be difficult, often requiring 4x4 vehicles. The terrain is rugged and marked by remnants of mining operations.
