The increase followed recent resource definition and extensional drilling of the Main, West and Sangar deposits, with mineralisation remaining open at depth and along strike, and the company anticipating additional resource growth once the drilling at the Yando and Danaya pegmatites is completed.
Executive director Greg Walker said the upgrade had exceeded expectations.
"At 32.9Mt, Goulamina was impressive. At 65Mt, it is even more so and clearly one of the world's outstanding hard rock lithium deposits," he said.
Walker said it was clear the full extent of Goulamina remains to be determined, but appeared to contain sufficient high-grade lithium-bearing pegmatite to justify a "significant mining development".
A maiden reserve statement and pre-feasibility update are due next month, with the company aiming to be in production by 2020.
It has already flagged significant savings in transport, handing and power costs, suggesting C1 costs should be below US$300/t.
Shares in the junior were up 8.7% to A56c, capitalising it at A$129 million.