People in the Cajamarca region say the proposed Conga mine will cause pollution and destroy water supplies.
The US-based mining company Newmont has promised modern reservoirs to replace threatened mountain lakes.
The dispute is a test for President Ollanta Humala, who has promised to continue mining development while protecting affected communities.
Mining is the main engine of Peru's booming economy, but it is also the cause of numerous social conflicts around the country.
http://www.bbc.co.uk/news/world-latin-america-15884119