Gold struck at New Zealand's deepest mine could be worth two-billion dollars.

The development —850 metres deep into the ground at The Snowy River Mine, near Ikamatua on the West Coast— is a bounty of quartz reef.

Development West Coast chief executive Heath Milne says that it's not a new discovery, but re-establishing an old reef that was mined in the 1950s.

Milne says it's been well known the resources were there, and after 70 million dollars spent getting to the old reef, the rewards are about to be reaped.

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