Probable ore reserves now stand at 10.35 million tonnes at 1.22% total rare earth oxide, including 0.43% neodymium and praseodymium.
The increase extends the proposed mine life at Yangibana by three years to 12 years.
It also increases the net present value to A$516 million.
The project also has an internal rate of return of 32% and payback period of two years.
Capital costs are expected to be $335 million.
German bank KFW-Ipex Bank has been appointed to provide up to $250 million in debt facilities.
Hastings said it was in discussions with a range of equity investors in Australia and Asia to raise a further $100 million, which is expected to be carried out in the next six months.
Shares in Hastings were unchanged at 16.5c, valuing the company at $128.3 million.