The Amazon rainforest has been plundered for decades for rubber, timber, and gold. Now, illegal prospectors are setting their sights on a new treasure: critical minerals coveted by much of the world.A new frontier of criminality is emerging in the Brazilian Amazon, authorities and experts say, with global demand for these minerals — used in many key products, like electric vehicles and fighter jets — setting off a rush of illicit mining in one of the planet’s most important ecosystems.This comes as the United States and other countries increasingly look to Brazil, home to some of the world’s largest deposits…