Plans to dredge a Coromandel harbour for gold and silver left over from the region's mining heyday have met opposition from locals, who fear it will release toxic substances into the pristine marine environment.
The Ministry of Economic Development has granted a prospecting permit to New Zealand company Sea Group Holdings to search McGregor Bay, just off Coromandel town, for the precious minerals.
The permit allows the company to explore 3.92sq km of harbour for the next two years, and take 80 core samples from the seabed.
Company director Marcus Jacobson said they would be sifting through the tailings - crushed-up rock and debris - dumped in the harbour 100 years ago by miners in the gold extraction process.
"The first step is just working out what's there and then it's about identifying the best method and approach. It could be dredging but it wouldn't be the whole harbour, it would only be a defined area and, again, we'd have to go through the resource consent process."
In the event that dredging or some other method of sediment extraction was allowed to proceed, it would be good for the harbour, he said.
"It's actually cleaning up the harbour at the same time."
This answer did not satisfy local kaumatua Betty Williams, of Ngati Maru and Ngati Pukenga.
"We were given a convoluted story that they were dredging it to clean the harbour and whatever gold they came across would be theirs," she said.
"They're not doing it for the sake of the harbour, they're doing it to make money and that's it, regardless of what they call it."
She was yet to meet other iwi leaders to see what they thought about the matter.
Green Party mining spokeswoman Catherine Delahunty said that it would be impossible to disturb the toxic materials in the harbour without damaging the environment.
"The mud, the sediment in the Coromandel harbour is known to be heavily impacted by previous mining.
"There may be some gold and silver but also heavy metals like zinc, mercury and arsenic, which are present when you crush up rock. You don't want to disturb those metals - they're toxic."
She said it would be the first time such work was undertaken in the harbour, however there had been dredging of tailings in other parts of the Coromandel.
Thames-Coromandel District Council chief executive David Hammond said moving from prospecting to actual extraction was a "massive" step.
"No doubt inside the harbours there's one heck of a lot of gold, but the question is whether it's in the marketable quantities to make it pay, that's what nobody knows.
"If these guys are going to do that they're really taking a punt, but conceptually the idea's interesting: take out all the contaminants and pay for that out of the gold that you extract and make a profit at the same time, but I don't know how you do that without disturbing a lot of other sediment on the seabed."
Sea Group Holdings was formed in November 2010 by Mr Jacobson and NZ Oil & Gas chief executive Andrew Knight.
Over the next two years, the prospecting permit allows Sea Group Holdings to complete:
*A database of all previous mining in the area.
*A bathymetric survey (GPS and echo-sounding) of the seabed using a survey vessel.
*A marine sediment thickness survey.
*Eighty core samples of 1m in length.
*Geochemical and geological analysis of these samples.