A Northland anti-mining group is urging locals not to engage with an Australian company planning to prospect for gold north of Whangarei.
Evolution Mining has bought the exploration licenses formerly held by De Grey Limited for Puhipuhi, and planned to begin geophysical survey work within the fortnight.
Minewatch Northland spokesman Tim Howard said locals should oppose the miners because of the risk they presented in an area with high mercury levels and heavy rainfall.
"It's the wettest area in Northland, it has the heaviest rainfall," Mr Howard said.
"Any mining in this territory will be releasing oxidised toxic minerals into those water systems."
Puhipuhi people should be cautious about meeting the company's officials, because they will then claim they have community support, Mr Howard said.
Evolution said it has had a constructive meeting with tangata whenua and residents.
Its chief geologist Roric Smith said the company was well aware the hilly area has heavy rainfall, and elevated mercury levels in places.
For mining to proceed, the company will have to show it can safely handle any risk posed by those factors, he said.
"We have actually got to understand and be able to plan, in the event we were to make a discovery, the type of ponds or other waste-drop dumps that would be capable of withstanding events that are well beyond the norm."