In the back yard of the federal police headquarters in Roraima, the northernmost state of Brazil, giant sacks lie strewn and overflowing with a jet-black, gravel-like mineral: cassiterite. Although less high-profile than other items seized during a crackdown on illegal mining in this Amazon state – including a Sikorsky S-76 helicopter painted in the colours of the Brazilian flag – cassiterite has become so sought-after that it is nicknamed “black gold”.
Cassiterite is the chief ore of tin, a less heralded but critical mineral for the energy transition. It is used in coatings for solar panels, lithium-ion batteries and solder for electronics, including wind turbines, mobile phones, computers and industrial alloys.
