The indicated and inferred resource now stands at 11.2 million tonnes at 1.21% lithium oxide and 40 parts per million tantalum pentoxide for 136,000 tonnes of contained lithium, up from 102,000t previously.
Just over half of the resource is in the indicated category.
The resource includes three mineralised pegmatites; Cade, Heller and Davy, which sit within 2km of each other.
"The Dome North mineral resource upgrade reflects the quality and excellent potential of the project and the outstanding results achieved from the three drilling program undertaken to date," Essential managing director Tim Spencer said.
"At this early stage, it is already possible to see a quality lithium project in the making with the right ingredients present in the form of multiple deposits, exploration upside, an easy development location and a fundamentally strong medium to long term outlook for lithium demand."
Metallurgical test work at the Cade deposit is underway.
"Completion of the first-pass metallurgical test work, expected late October, will be important to understand an optimal process route and the related cost parameters," Spencer said.
Dome North is part of the Pioneer Dome project, which also includes the Sinclair caesium deposit.
The company is awaiting assays for drilling to the north of Sinclair, where visual crystalline pollucite was intersected in one of three zones tested.
Essential, formerly known as Pioneer Resources, also has 51% of the Mavis Lake lithium project in Canada, two gold projects outside Kalgoorlie, a nickel project, and farm-ins with Northern Star Resources, Novo Resources Corp and Black Cat Syndicate.
Shares in Essential have risen about 30% in the past two sessions, but were down 7.1% today to 13c, valuing the company at $19.6 million.