Blackstone MD Scott Williamson gave the broad estimate in response to a question after he presented at the NWR Virtual Resources Conference last week.

Of that total, about $100 million could comprise the cost of the nickel sulphate refinery, with the recent arrival on the Blackstone-scene of South Korean battery company EcoPro a potential case-in-point regarding future funding.

Last month EcoPro invested in Blackstone at a premium and agreed to form an alliance whereby the next stage of the partnership "will be an additional investment via a joint venture agreement to develop the downstream processing infrastructure project".

Upstream, the cost of refurbishing the concentrator and getting a mine underway at Ta Khoa could be $50-100 million, though again, it's very early days in terms of capital estimates.

Meanwhile, Williamson suggested a big plus for Blackstone with the discovery of the King Cobra nickel prospect was the presence of platinum, palladium, gold and rhodium - offering significant potential for by-product credits.

Scoping results and a maiden resource for King Cobra and Ban Phuc at Ta Khoa is expected next quarter.

Shares in Blackstone were trading at A15c this week, capitalising the company at $29 million.