Geologist challenges 'keyhole' mining claims

University of Otago geology professor Dave Craw said that gold was richer and easier to get at in Coromandel. Photo / Greg Bowker

Strong pressure to mine the Coromandel Peninsula is inevitable if legal protection is lifted - and it would be better if the mining was in open pits, says a geologist.

University of Otago geology professor Dave Craw said "surgical" mining techniques proposed by the Government to protect the environment were too inefficient because they took only the easiest gold.

Gold deposits such as those under the Coromandel had a rich core, said Professor Craw. But the lower-grade stuff at the margins was where the "real money was made".

He said one large open-cast mine would be better than four or five small underground mines accessed by "keyhole" cuts that took the richest ore and left the rest behind.

Coromandel had a similar history to Reefton on the West Coast of the South Island, where there was open-pit mining on conservation land, said Professor Craw.

Because of local opposition, mining had been banned in Coromandel but not Reefton, he said. But the gold was richer and easier to get at in Coromandel.

"Eventually there will be much more pressure to go back into Coromandel."

Prime Minister John Key has ruled out open-cast pits in the Coromandel and on Great Barrier Island under Government proposals to open some conservation land to mining.

Conservationists are worried that it may not be economic to mine for gold without more huge open-cast mines like Martha Mine at Waihi, with its 40 million tonnes of tailings.

Professor Craw said "surgical" mines produced less waste rock than open pits, meaning less mess for the community to deal with. But they were less efficient in getting the minerals out.

Massey University professor of resource and environmental economics Anton Meister said that even a small mine in the country's most precious conservation land would be like a "pimple on a perfectly smooth-skinned face - the pimple destroys the overall effect".

Professor Meister said tourists were attracted to high-value conservation land protected from mining because of its unspoiled looks.

There was no way to tell how much mining those places could bear without affecting the $21 billion tourism industry, he said.

It has been estimated that $194 billion of minerals is under the more than 7000ha of conservation land the Government wants to open for mining in the Coromandel, Great Barrier Island and parts of the South Island's Paparoa National Park.

But Professor Craw said that was based on "intelligent guesses" by geologists and the true amount could easily be $50 billion or $500 billion.

He said little was known about whether the land could be mined at a profit. "We really have no idea."

In the short term, it was unlikely the mining industry would "pull us out of the economic doldrums", he said. "Getting a mine started in New Zealand takes about 10 years."

Although the profits were uncertain, Professor Craw said the long-term economic benefits of mining to nearby towns and cities were greater than anti-mining groups made out.

Meanwhile, Gavin Mudd of Monash University in Melbourne said the environmental footprint of mining was becoming bigger around the world as the quality of ore left in the ground fell - requiring bigger operations, using more energy to get it out.

He said it was difficult to measure the environmental cost of a mine until after it was closed and the land rehabilitated.

Energy and Resources Minister Gerry Brownlee has announced a three-week extension for public submissions on the mining proposals. They will now close on May 26.

GOLD FEVER

* One large open-cast mine in the Coromandel would be preferable to four or five small underground mines, a professor of geology says.
* Surgical mining techniques proposed by the Government take the richest ore and leave the rest behind.
* They produce less waste rock than open pits but are less efficient in getting the minerals out.
* It has been estimated that $194 billion of minerals is in more than 7000ha of conservation land the Government wants to open for mining.