Base has estimated the Kwale North Dune totals 171 million tonnes at a heavy mineral grade of 1.5%, based on a 1% HM cut-off.

Of that total, 136Mt at 2.1% HM is in the indicated resource category.

Drilling of the deposit is set to continue in 2019, while a "concept study" is set to kick-off shortly.

The Kwale operation is currently based on the Central Dune and South Dune deposits, with mining operations to date focused on the Central Dune.

A transition to the South Dune deposit is scheduled for next month, and on current ore reserves, Kwale will continue operated until mid-2022 - extended to mid-2024 subject to approval of the South Dune mining lease variation currently before the Kenyan government.

With regards a broad comparison, measured and indicated resources at the Central Dune were estimated at 76.2Mt at 6.1% HM when the project was being developed early this decade, while at the South Dune there was 69Mt at 3.6 HM.

Meanwhile a definitive feasibility study is underway in Madagascar on Base's Toliara where construction could begin in earnest next year.

Shares in Base were up 2% to 27c in afternoon trade, capitalising the company at $315 million.