The resource calculation was completed as part of the front-end engineering and design program for the proposed development, which is looking to make a final investment decision next year, and includes data from the recent 10,792m mine development drilling program.
The resources are spread over the Kundu, Lando, Tongo Dyke and Pandebu kimberlites, with the largest being 3Mct at Lando with an average grade of 2.9ct and 2.8Mct at 3.2ct at Kundu.
Around one quarter of the resources, 1.9Mct, is classified as indicated.
Executive director Mike Lynn said the update revealed "a robust indicated and inferred diamond resource" early in Newfield's work program at Tongo.
"The diamond grades and values, in particular for the Kundu and Lando kimberlites, point to some of the most impressive kimberlites globally on a dollar per tonne rock value basis," he said.
"The updated resource estimate is also predominantly limited to a depth of just 230m from surface.
"Previous deeper drilling has shown that these kimberlites extend to much greater depths which, along with the clear potential from other identified kimberlites on the project, would suggest the global resource could be significantly increased in the future with more evaluation work.
"It is for this reason that we have previously described the Tongo project as a potential generational asset."
Mine optimisation as part of the FEED program continues, with the work on the Kundu, Lando and Tongo-Dyke-1 kimberlites expected to be completed this quarter.
Underground mining is planned to focus on those kimberlites, however Pandebu has also been drilled as it is adjacent to Lando and could be readily incorporated into future mine planning. Previous mining of a kimberlite blow associated with Pandebu yielded over 18,000ct of high value diamonds.
A 5tph bulk sampling plant has recovered high grade diamonds in recent months, allowing Newfield to sell its first diamonds, and Newfield recently completed the breakdown of a 50tph processing plant and has relocated it from the Koidu mine site to Tongo, where it will be redesigned and upgraded.
Tongo comprises two adjacent mining licences covering a combined 134sq.km. There are seven additional kimberlites at Tongo not included in the resources.
Newfield shares jumped 33% on the news, hitting 16c, increasing its market value to $93 million.
The company has recovered more ground since hitting a low of 10c in October. Over the past year its shares have slumped from around 30c following a massive capital raising and the dilution associated with the merger with AIM-listed Stellar Diamonds, aimed at funding the Tongo-Tonguma development.
