The agency said that the death last year of a large cluster of the flowers — likely caused by squirrels gnawing roots for water — along with the mine’s development, would reduce the flower’s population by at least 70%.

The Center for Biological Diversity (CBD) sued US regulators in 2019 for granting ioneer exploration permits, arguing that ioneer’s project would disturb the rare flower.

The CBD withdrew its suit in January 2020 after ioneer agreed to take additional measures to avoid the plant, but the environmental group has vowed to closely monitor the project.

ioneer published the definitive feasibility study for Rhyolite last year, forecasting cash costs of about $2,510 per tonne of lithium carbonate.

The mine is expected to operate for at least 26 years, producing about 20,600 tonnes of lithium carbonate annually, once it begins production in 2023.