The project will now move to an exploration phase, developing a 3.3km tunnel to get access for more underground test drilling to better define the gold content, before a final decision is made on whether to begin mining.
Capital of $US30million ($NZ44.3million) is being sought, which would cover the cost of the tunnel and exploration drilling, Tasman's managing director Mark Le Messurier said when contacted in Sydney yesterday.
"I've spoken to several [Australian] groups, private investors and private equity funds, but have some New Zealand investors to talk with in the new year," he said, declining to identify them as yet.
"The reality is the challenge to raise the funds for the decline.
"It needs more drilling to prove the quality of the ore body ... so investors will have confidence to invest," he said.
Blackwater, which in recent years has had $18 million spent on exploration, is 37km south of Reefton, beneath the abandoned township of Waiuta, in the foothills of the Victoria Range.
Oceana Gold still owns the mine, but should Mr Le Messurier decide to go ahead he has an option to buy.
From 1908, until the shaft collapsed and the mine closed in 1951, it produced about 750,000oz of gold, going to depths of about 1000m underground.
Estimates of the gold still there range from 580,000oz up to about 700,000oz.
When asked, Mr Le Messurier said the deadline to raise the capital for the tunnel and exploration drilling was by December next year.
The decline, or tunnel, begins on private land and goes towards the ore body at a 1:7 gradient, in a straight line.
He noted one previous test hole of Oceana's was a "very expensive" 1.6km long, prompting the need to go underground and drill from those depths.
Should a decision to go ahead be made, the company would then seek $US40million to go into production, which would include a nearby processing plant to extract the gold and smelt into rough "dore" bars.
The figure of $US500million was the "all up" cost of establishing the mine and included costs to operate it for a decade, he said.
He confirmed government permitting agency New Zealand Petroleum and Minerals had granted a 20-year mining permit for Blackwater.
"The mine would have a small surface footprint with an access point and infrastructure located on private land several kilometres away from the historic mine site," he said.
Tasman Mining would next seek final approval for its annual work plan and environmental management plans from the Buller and West Coast Regional Council.
Mr Le Messurier hoped surface preparation of the mine could begin by mid-2019.
He estimated the decline would take two years to build, employing about 30 people, and then a further two to three years to get into production, employing about 100.
Tasman has appointed Nigel Slonker as Blackwater's project manager, including site preparation and decline development.
He is an experienced underground mining engineer, previously working as a mines, tunnels and quarries inspector for WorkSafe New Zealand and was Oceana Gold's general manager at its now closed Reefton gold mine and mining manager of its Frasers underground mine at Macraes, in East Otago.
