The measured and indicated resource has increased from 372.4Mt in the company's 2017 resource statement to 413.4Mt at 0.47% lithium oxide and 0.05% tin, while the total resource has risen by 12.3Mt to 708.2Mt at 0.43% lithium oxide and 0.05% tin (0.1% lithium or 0.2153% lithium oxide cut-off).
The upgrade follows a 22-hole drilling program, the results of which executive chairman Keith Coughlan said had been "in line with or better than expected".
"The primary stated aim of this drilling program was to convert a larger portion of the resource to the measured category to provide greater certainty of the financial model and security to financiers," said Coughlan.
"The results clearly indicate that the program has been successful and the robustness and consistency of the Cinovec resource further demonstrated.
"As we move closer to ultimate financing and offtake discussions, this higher degree of certainty provides more funding options for the project," he added.
Analysts at WH Ireland said increasing the measured and indicated resource "allows for much more detailed mine planning for the first years of mine life".
European Metals shares closed at A$1.375 in Australia yesterday, valuing the company at $242 million. The stock rose 3% in London yesterday to 70p.