Rio Celeste is a gorgeous Costa Rican river with a length that's famous for its unusual turquoise waters. After decades of guessing, scientists finally determined the cause was aluminosilicate:
Via Oddity Central:
"Sunlight contains the entire color spectrum, similar to the way we see them all in a rainbow. In any other river sunlight penetrates to a certain depth and no particular color is deflected or reflected back to the surface, so it looks transparent, while in the Río Celeste the water passes some of the Sun's rays, but reflects the bluish tone group. So the water appears blue to the human eye."