An anti-mining group has blocked trucks and workers from entering the Karangahake Gorge.

Photo: 123RF

New Talisman Gold Mines announced last week it had found over 8500kg of high-quality gold at its Dubbo site in the gorge at the southern end of the Coromandel.

The company's chief executive, Matthew Hill, said the finding offers a significant opportunity for New Zealand.

"The grades that have come out show 21 grams a tonne which is in today's terms one of the top five or certainly one of the top ten in the world."

He said the company was still prospecting but it was intending to trigger its resource consent to start bulk sampling. From there the results would be put to the company's board to decide the next step and whether to start mining.

Environmental group Protect Karangahake said it was concerned about the impact the mining would have on the environment.

"The Conservation estate is important. It's precious for New Zealand and it's not to be divvied and sold off for gold mining industry because they will do nothing but destroy it.

"As we know in the past in Karangahake they devastate the area once the mining starts."

Protect Karangahake had 30 people blocking access to the site for an hour and a half this morning.

Its chair, Duncan Shearer, said they were doubling their efforts to protect the gorge.

"Usually two or three times a week we'll be a presence on the mountain, sometimes just noting what's happening in the sense of vehicle movements.

"Sometimes walking up the mountain track, holding up the vehicles as we walk up the hill to enjoy the beautiful view. Sometimes we're doing these big protests that get arranged at quite short notice."

Mr Searer said protesters were warned by police this morning but moved when asked.

However, Mr Hill said the environmental impacts Protect Karangahake was worried about would be small.

"The footprint above surface where disturbances occur is a very small - less than 0.4 hectares. It's been closed off since 1995 and was only opened for 12 months.

"Most, if not 95 percent of our disturbances occur deep underground and will not be noticed at the surface level.

"Our current resource consent, four 10-tonne trucks a day, is hardly going to make an impact in comparison with the trucks rolling down SH2.