A new resource estimate for the Sonora lithium project in Mexico has more than doubled the contained metal amount, Rare Earth Minerals (LON:REM) told investors.

The study by consultant SRK, which used 3D modelling, also identified a further exploration target, which has the potential to add up to a further 4.6mln tonnes of lithium carbonate equivalent (LCE).

Chairman David Lenigas said: "The size of the Sonora Lithium Project as a whole has grown significantly since the last resource update to a combined indicated and inferred resource of 7.42 million tonnes of LCE, 226% larger than previously reported, thanks to a number of successful drilling campaigns.

"Further drilling, if successful, has the potential to add a further 2.4 - 4.6 million tonnes of LCE within the defined SRK pit shell from conceptual extensions and Sonora still has further upside to be tested at the new Buenavista concession and elsewhere on the Sonora concession package."

In the higher confidence indicated category is now 1.12 million tonnes (Mt) of LCE contained in 95 Mt of clay, at lithium grade of 2,200 ppm (parts per million), while the inferred portion has 6.3 Mt of LCE contained in 500 Mt of clay at a grade of 2,300 ppm.

The indicated portion will be used for initial open pit mine design while the group further develops the inferred resource, it said.

Conceptual extensions within the current pit shell have the potential to add 2.4 to 4.6 Mt of LCE contained in 300 to 250 Mt of clay at a lithium grade of around 1,500 to 2,500 ppm, the group added.

Bacanora, in which the firm holds a 15.4% stake, is Rare Earth's joint venture partner on the Sonora project.

REM also has a 30% direct interest in the Fleur - El Sauz and Megalit joint ventures on the property. It means REM now has a total economic interest in each of these ventures of 40.78%.

SP Angel highlighted in a note that 64% of the world’s reserves and 39% of production of lithium carbonate are contained in Chile and Argentina making diversity of supply a priority for strategic agencies around the world.

Elsewhere, broker VSA Capital noted that the clay resource compared "favourably in grade with clay resources being exploited in China and the rest of the world".

"It will likely attract increasing attention from the leading lithium chemical although is still some years away from production, in our view," said the broker."

Shares eased 1.72% to 1.145p.