The defined resource is now 75.5 million tonnes, with grades averaging 99.16%, based on a 98.5% cut-off grade.
It is another significant jump in Galalar, which increased total resources 30% to 62Mt in March.
Galalar's resources now over some 486 hectares, and is described as a continuous, world‐class, high‐purity resource.
The resource has an average thickness of 15.5m. Some 66Mt are in the measured and indicated categories, with 9.2Mt being inferred.
Diatreme sees Galalar as being a similar long-life operation to the adjacent 3Mtpa Cape Flattery mine, which has operated since the 1960s.
It has a mining lease application lodged with the state government that entirely covers the resource.
A definitive feasibility study and draft environmental impact statement are being finalised, with the company anticipating first production in late 2022.
In tandem with its development plans, initial exploration over two nearby targets continue to suggest the potential for significant future growth.
The company has only been working on Galalar since 2016, having previously focused on its zircon rich Cyclone project in Western Australia's Eucla Basin.
Diatreme is well capitalised to advance Galalar, having just raised A$10 million at 2.3c with Euroz Hartleys to carry it through to completion of the DFS, permitting and examination of the Nob Point barge ramp and Cape Flattery Port export solutions.
The company already has offtake agreements with three Chinese firms for up to 750,000tpa of product.
Diatreme's shares, which have traded between 1-3.1c over the past year, and closed at 2.3c on Friday, valuing it at $69 million.