Save Foulden Maar spokesman Shane Loader was delighted the site was now in public ownership, protecting it for future generations and probably ending any realistic chance of mining there.
"To see the mining rights extinguished and the land purchased by Dunedin City Council is an incredible outcome for everyone involved in the campaign," Mr Loader said.
"So many people didn’t think we could win this fight, and we did."
Negotiations ended up taking just over three years and collection of material for scientific research was also suspended.
Mr Loader said he grew anxious for a resolution that had now been secured.
However, public access is not yet permitted and it is understood this is to be looked into.
The purchase of about 42ha of land from the receivers of mining company Plaman Resources was on commercial terms for $924,000, the council said.
This was made up of $864,000 for the land and mining permit and $60,000 for entitlements under the Public Works Act.
Receivers Neale Jackson and Brendon Gibson, of Calibre Partners, surrendered the mining permits relating to the property.
The city council confirmed its intention to preserve the property for environmental and scientific research purposes.
Council chief executive Sandy Graham said Foulden Maar was a globally significant site, considered by scientists to contain New Zealand’s richest trove of fossils.
"The council has been working since 2019 to protect the significance of Foulden Maar," Ms Graham said.
"We’re delighted to have reached this agreement, which will prevent any mining taking place and preserve this very special scientific and conservation site into the future."
Plaman Resources had wanted to mine diatomite, but it went into receivership in 2019.
Foulden Maar formed after a volcanic eruption dated to 23 million years ago and diatomite deposits accumulated.
University of Otago geologist honorary associate professor Daphne Lee said a valuable climate record was preserved there.
She was looking forward to being allowed to resume collecting material to study, once permission was granted, she said.
She also hoped to take research students to the site.
