The West Rolleston resources soared by 361% to 369.1 million tonnes, while the Vermont East-Willunga resources jumped 202% to 497.6Mt.

Macarthur owns significant stakes of both projects, with 90% of West Rolleston and 85% of Vermont East-Willunga.

While both projects do not yet host any reserves, Vermont East-Willunga holds 170Mt of measured resources while West Rolleston is home to 47.2Mt in this category.

Macarthur chief executive Nicole Hollows said the company is committed to exploring and evaluating its large portfolio of greenfield opportunities.

“We have recently committed $25 million per year to explore and understand our existing portfolio of coal tenements,” she said.

“Exploration field and laboratory work is an ongoing investment for the company and the increase in resource at both Vermont East-Willunga and West Rolleston is testament to the potential growth within the portfolio.”

The mines and projects operated by Macarthur host a total of 654.8Mt of measured resources, while proved coal reserves total 179.5Mt.

Macarthur shares closed up 6.8% to $11.78.