Encounter Resources (ASX:ENR) said metallurgical test work for the Green deposit within its Aileron Project in Western Australia has returned recoveries of 51% to 53% on representative head grades of 2.2% to 2.8% niobium pentoxide, according to a Monday Australian bourse filing.

The company said the test work achieved up to 57% niobium pentoxide concentrate grade post refining, an industry-standard result, with the flowsheet and results comparable to existing niobium operations, the filing added.

Next steps include test work to produce ferroniobium and niobium oxide, as well as optimization work targeting enhanced recoveries and concentrate grade, it added.

The company's shares fell 7% in recent Monday trade.