Diamond mining in Brazil, historical artwork. Slaves working to excavate and wash ores at a diamond mine in Brazil. Overseers with whips are controlling the mining operation, one with a parasol and a dog, another under a shelter. Diamond mining in Brazil began under the Portuguese in 1725. Large amounts of diamonds were mined by slave labour imported from Africa. The alluvial mining shown here involved excavating and washing diamantiferous sands and gravel known as cascalhao. Artwork from the third edition of 'Les Entrailles de la Terre' (1902) by French author Eugene Caustier.