The company, headed up by Australia's former treasurer, estimates its Northern project has almost doubled in size, rising 89% from 124 million tonnes to 235Mt, including an upgraded indicated resource of 103Mt.
Northern is now three times larger than the more advanced 75.5Mt Galalar resource to the south and gives Diatreme some 310Mt in total resources.
The latest upgrade emerged from 188 holes for 1845m completed late last year, defining dunes that have average thicknesses of 12m, with some up to 55m thick.
Encouragingly, the Si2 dune complex remains open to the south and north along, and Diatreme is confident of growing resources further as it seeks to become a key supplier of high-grade silica sand to Asia's solar panel producers.
A scoping study is being finalised for Si2, with feasibility studies expected to follow, as Diatreme seeks to fast-track development of its second mining operation, using the state-owned Cape Flattery Port for exports.
Recent hand auger drilling at the northern end of the Casuarina dune system, currently mined by Mitsubishi's at the long-lived Cape Flattery operation, has also indicated potential for additional mineralisation similar to those at Si2.
Diatreme was also continuing negotiations with the Hopevale Congress and Walmbaar aboriginal corporations.
Last December The Australian reported the mining proposal had split local traditional owner groups and that, counter to Diatreme's claims, it did not have full support of traditional owners.
Further, the newspaper reported that federal regulators issued a show cause notice against the Hopevale Congress alleging it was riddled with governance failures, financial mismanagement and was not representative of the region's 13 native title clans.
Diatreme said there were "numerous inaccuracies and speculation" in the article, noting that Hopevale's independent legal counsel reported that at meetings attended by over 150 Thiithaar and Gamaay traditional owners there was more than 95% of attendees supporting the Galalar development.
The company is backed by material solutions company, Sibelco, which is investing up to A$35 million.
Diatreme shares, which have traded at 2-4.6c over the past year were up 4% this morning 2.8c, valuing it at $104 million.
