The mine produced 12,657 ounces of gold during the quarter, 1% higher year-on-year and 2% below the strong March quarter.

This brought total output for the first half of 2018 to 25,582oz, slightly ahead of the 25,316oz produced a year ago, allowing the company to maintain its full-year guidance of 55,000-59,000oz.

Caledonia said the Blanket mine remained on track to reach 80,000oz by 2021.

CEO Steve Curtis commented that grade during the June quarter was below expectations, due to a combination of normal variations in the orebody and some modified mining practices to improve safety, although grades had since reverted to budgeted levels.

He added sinking of Blanket's central shaft was continuing according to plan and within budget, with the shaft currently at a depth of 1,073m, although sinking had been paused due to the process of cutting stations for horizontal development at depth.

"The project continues to progress well and we look forward to commencing production from the central shaft in 2020 which is expected to deliver the Company's growth plan to achieve 80,000 ounces by 2021," he said.

In London, Caledonia's shares were trading at £6.225 (US$8.23) Thursday, down 0.76%.