Sovereign Metals (ASX:SVM) said geotechnical investigations are being conducted at key project infrastructure locations across its Kasiya rutile-graphite project in Malawi, and the results will be used to support the layout and engineering design for the definitive feasibility study, according to a Wednesday Australian bourse filing.

The study is due in the fourth quarter. Upon announcement of the study results and under an investment agreement, Rio Tinto (ASX:RIO) will have up to 180 days to exercise its option to become the operator of the project and be granted exclusive marketing rights for 40% of the project's annual production.

The firm anticipates producing a 96% graphite concentrate at the project at an incremental cost of $241 per tonne.

During the March quarter, rehabilitation of land at the test pit site mined at the project during the pilot mining and land rehabilitation phase was substantially progressed.

Its shares fell over 2% in recent trading on Wednesday.