Walkabout increased the proven and probable ore reserve by 10% to 5.5 million tonnes, with the total graphite content (TGC) up 22% to 987,000t and the life of mine grade up 11% to 17.9% TGC.
Executive director Allan Mulligan pointed out that "grade is king" and the company had validated Lindi Jumbo as the highest-grade graphite project in Walkabout's ASX-listed, East Africa-operating peer group.
The company said the higher-grade would also allow better operational efficiency, with a 13% reduction in required throughput while maintaining annual production of 40,000 tonnes of flake graphite.
"The super-high-grade mill feed means that Lindi Jumbo is an incredibly robust project and positions the company to deliver the largest margins in the industry," Mulligan said.
He said Walkabout would now be able to take advantage of opportunities for increased market share and it would continue towards its goal of become "the non-China producer-of-choice for premium large-flake natural graphite".
An updated definitive feasibility study is due shortly.
"We expect the upcoming amended DFS will reflect an improvement in the already strong project economics when it is released as the high grade mineralisation is close to the ROM pad at the proposed plant which could translate into lower operating costs in the initial years of production," Patersons Securities analyst Cam Hardie said.
"As a reminder, the updated DFS released in August 2017 contained start-up capital of US$29.6 million, ongoing capex of $5.76 million, a product weighted average basket price of $1564/t, and a post-tax NPV of $180 million with an IRR of 88%."
Patersons maintained a speculative buy rating and A20 price target.
Walkabout's shares rose 4.7% on the news yesterdayu to 11c, up 22.2% since the start of 2019.