Two-thirds of the resource is in the measured or indicated category, with Core suggesting "considerable scope" remains to further increase the resource.
Located on Darwin's doorstep, Finniss is being assessed as a 1 million tonne per annum processing operation, with the prefeasibility study completed back in June outlining a mine life of 26 months.
The capital cost of the project was previously estimated at A$53.5 million, with output of 225,000tpa of spodumene concentrate grading 5% lithium oxide.
Core is estimated to currently have about $6 million cash.
Shares in Core were up 4% to 5.3c in morning trade, capitalising the company at $33.5 million.
The stock started 2018 at about 9c.