The sight bluish green water flowing through the Boac River in Marinduque province has raised suspicions of a high level of acid seeping from mine wastes left in the defunct Marcopper mining site. But Roland de Jesus, regional director of the Mines and Geosciences Bureau, described an acid mine drain as a "natural occurrence," especially in areas with large deposits of copper. Copper ore, when submerged in water, becomes acidic giving off the bluish green color.

Cinco, M. (2016, September 2). Marinduque town fears lingering mine effects. Philippine Daily Inquirer, p. A8.